Active Learning In Chemistry Education - Potomac School

Active Learning
In
Chemistry Education
"ALICE"
Al
I
Ce
Copyright 1997, A.J.Girondi
505 Latshmere Drive
Harrisburg, PA 17109
alicechem@geocities.com
www.geocities.com/Athens/Oracle/2041

NAME________________________________ PER ________ DATE DUE ___________________
ACTIVE LEARNING IN CHEMISTRY EDUCATION
CHAPTER 25
INTRODUCTION
TO ORGANIC
COMPOUNDS
(Part 1)
25-1 ©1997, A.J. Girondi

NOTICE OF RIGHTS
All rights reserved. No part of this document may be reproduced or transmitted in any form by any means,
electronic, mechanical, photocopying, or otherwise, without the prior written permission of the author.
Copies of this document may be made free of charge for use in public or nonprofit private educational
institutions provided that permission is obtained from the author . Please indicate the name and address
of the institution where use is anticipated.
© 1997 A.J. Girondi, Ph.D.
505 Latshmere Drive
Harrisburg, PA 17109
alicechem@geocities.com
Website: www.geocities.com/Athens/Oracle/2041
25-2 ©1997, A.J. Girondi

SECTION 25.1 Introduction to Carbon Compounds
All substances can be classified as being either organic or inorganic. So far, our study of
chemistry has dealt mainly with inorganic compounds. Originally, organic substances were considered to
be those carbon compounds that were extracted from living things, while inorganic ones were
compounds that did not originate in living systems. An organic compound is defined as a substance that
contains the element carbon. However, some compounds that contain carbon are considered to be
inorganic. A better definition may be that organic compounds have a carbon base, that carbon is the
"backbone" of the compounds.
Organic chemistry plays a very important role in our daily lives. Many of the clothes we wear are
made of rayon, dacron, nylon and orlon. These are all synthetic (man-made) organic compounds. Plastics
of all sorts are synthetic organic compounds, too. Petroleum is a naturally occurring organic substance,
but synthetic rubber and plastics are two of the by-products of petroleum.
A large number of modern chemical materials have been developed from by-products of
petroleum. In addition to these items, other materials such as sulfa drugs, penicillin, cortisone, perfumes,
detergents, vitamins, pesticides, anesthetics, and many of the more modern antibiotics are among the
contributions made to society through a study of organic chemistry.
Throughout the 18th century, early chemists unsuccessfully tried to synthesize organic
substances, starting with inorganic materials in their laboratories. Their failures gave rise to the "vital force
theory" which stated that organic compounds could only be produced by a "vital force" which was
responsible for life itself. This conclusion was closely tied to religious beliefs at the time. However, in
1828, the German chemist, Friedrich Wohler, succeeded in synthesizing an organic compound known as
urea, starting with two inorganic compounds. Thereafter, many other organic compounds were
synthesized in the same way in laboratories around the world. By 1850, the "vital force theory" was
discredited. From that time on, organic and inorganic chemistry were recognized as two major fields of the
science. There are over 90,000 known inorganic compounds. However, there are well over one million
known organic compounds, and many more are being synthesized by chemists every year!
Why are there so many organic compounds? Well, carbon atoms can attach themselves to each
other in wide variety of ways. They can join together to form short or long chains, and they can form rings
of many kinds, as well:
C
C
C– C– C
C
C
C C C C C
C
C–C–C– C– C–C C–C–C–C–C C C C C C C
Carbon Chains
Carbon Rings
The chains and rings can have branches and cross-links with atoms of other elements (mainly hydrogen)
attached to the carbon atoms. Different arrangements of carbon atoms correspond to different
compounds, and each compound has its own characteristic properties.
We are going to approach the subject of organic chemistry in terms of organic nomenclature.
Nomenclature involves the naming of compounds. We will restrict ourselves to the simpler organic
compounds, because the more complex ones can get really complicated. You will be given a set of rules
to follow as you name compounds. These rules must be followed very carefully. Success in learning
organic nomenclature will involve some memorization on your part, but it will rely mainly on a logical
approach to the problems presented.
The second most abundant element found in organic compounds is hydrogen. This chapter will
deal exclusively with compounds composed of only carbon and hydrogen. These are called
25-3 ©1997, A.J. Girondi

hydrocarbons. These two elements can combine in countless ways. The structures of some
hydrocarbons are shown below. The lines between the atomic symbols represent bonds. There are
three types of carbon to carbon bonds:
H
H C C H
H
H
H
C
C
H
H
H
C C H
single bond double bond triple bond
In each case you will note that carbon has a total of four bonds. This is because carbon
has four valence electrons. There are only a few carbon compounds in which carbon
does not have four bonds. One example is carbon monoxide. In this chapter,
however, we will deal only with organic compounds in which the carbon atoms have
four bonds. After we have studied the hydrocarbons, Chapters 26 and 27 will
introduce you to the names and structures of organic compounds which contain other
elements in addition to carbon and hydrogen.
C
O
carbon
monoxide
Section 25.2
The Alkanes
The alkane family represents the simplest of the hydrocarbons. The general formula for the
compounds in this family is CnH2n+2, where "n" equals the number of carbon atoms in the molecule. For
example, if you substitute a 1 into this formula you will get CH4. Substitute a 2 and you will get C2H6.
These are the first two members of the family. The compounds in the alkane family are often called
saturated compounds, which means that the molecules contain only single bonds between the carbon
atoms.
Naming alkanes is fairly simple. The prefix in the name of each compound indicates the number of
carbon atoms present. All alkanes have a suffix of -ane. A list of alkane prefixes is shown in Problem 1
which has been partially completed for you. To make writing formulas or drawing structures easier, the
hydrogens on the carbons are not always shown (note the structures on page 25-3); however, you should
assume that enough hydrogen atoms are present to give each carbon atom 4 bonds.
Problem 1. Give the name and molecular formula for each compound below. Use the formula CnH2n+2
to determine the formula, and add the suffix "ane" to the prefixes to obtain the names.
Prefix No. of Carbons Name Molecular Formula
a. meth- 1 ___methane__ ____CH4___
b. eth- 2 ____________ __________
c. prop- 3 ____________ ____C3H8___
d. but- 4 ____________ __________
e. pent- 5 ___pentane___ __________
f. hex- 6 ____________ __________
g. hept- 7 ____________ __________
25-4 ©1997, A.J. Girondi

h. oct- 8 ____________ __________
i. non- 9 ____________ __________
j. dec- 10 ____________ ___C10H22__
In problem 1, you were writing molecular formulas. The kinds of formulas seen at the top of page
25-4 are known as structural formulas. Writing structural formulas for organic compounds can become very
cumbersome when all of the chemical bonds are included in the drawings. To remedy this problem,
chemists have developed a shorthand method of writing structural formulas that involves condensing the
structures. In this shorthand method, the carbon atoms are still written separately (separated by hyphens),
but the hydrogens which are bound to carbons are not. Instead, the hydrogens are written to the right of
the carbon atoms to which they are bonded. This method of representing organic compounds is known
as the condensed structural formula. Study the examples of condensed structural formulas below.
Compound Molecular Formula Structural Formula Condensed Structural Formula
methane
CH4
H
H
C– H
CH4
H
butane
C4H10
H
H H H H
C–C–C–C– H
CH3-CH2-CH2-CH3
H H H H
Problem 2. Complete the exercise below.
Compound Name Molecular Formula Condensed Structural Formula
a. methane ______CH4______ _____________CH4_____________
b. ethane _______________ _____________________________
c. propane _______________ _____________________________
d. butane _____C4H10______ ________CH3-CH2-CH2-CH3________
e. pentane _______________ _____________________________
f. hexane _______________ _____________________________
g. heptane _______________ _____________________________
h. octane _______________ _____________________________
i. nonane _______________ _____________________________
j. decane _______________ _____________________________
25-5 ©1997, A.J. Girondi

Section 25.3 Alkyl Groups
Carbon chains are not rigid structures. They can bend and flex freely. When we say that an alkane
has a "straight" chain, we don't really mean straight. We mean that it is a continuous chain, rather than a
branched chain. The two structures below both contain six carbon atoms. The one on the left is
"straight," while the one on the right is branched.
CH3
CH2 CH2 CH2
CH2
CH3
CH3 CH2 CH2 CH CH3
CH3
This is one continuous
chain of carbon atoms.
This is a branched
chain of carbon atoms.
Now that you have mastered the straight-chain (or should we say "continuous" chain) alkanes, it is
time to try something more challenging. Most alkanes exist as "branched" molecules such as the one
shown below. The longest continuous chain of carbon atoms in the molecule below is 7 (enclosed by
box). Therefore, the parent compound here is heptane. (Remember, the longest continuous chain is not
necessarily straight!)
CH2
CH3
CH3 CH2 CH2 CH CH CH3
CH2 CH3
The longest continuous chain contains 7 carbon's.
Having identified the parent compound, we must next identify the side chains. These side chains are
commonly called alkyl groups. Alkyl groups are attached to the longest continuous chain. When written
alone, they are usually shown with a free-bonding site represented by a dash (like this: –CH3). This
bonding site represents a spot where a hydrogen atom has been removed. Thus, the general formula for
the alkyl groups is CnH2n+1. The free bonding site is what allows the alkyl group to bond to the parent
compound. Alkyl groups are named with the same prefixes as the alkanes themselves. The suffix is
changed from "ane" to "yl." Complete Problem 3 below by entering the formulas and condensed
structural formulas of the first six alkyl groups.
Problem 3. Complete the exercise below.
Name of Alkyl group Condensed Structural Formula
a. ___methyl _____________–CH3____________
b. __________ _____________________________
c. __________ _____________________________
d. ___butyl___ ________–CH2–CH2–CH2–CH3_____
e. __________ _____________________________
f. __________ _____________________________
25-6 ©1997, A.J. Girondi

Depending on where the hydrogen atom is removed, the bonding site on some alkyl groups can change
position. This would change the way in which the alkyl group bonds to the parent compound. For
example, note the two alkyl groups shown below. Both are composed of three-carbon chains, but the
bonding site differs:
CH2 CH2 CH3 CH3 CH CH3
propyl
isopropyl
The compound on the left below has a propyl group attached to the parent compound which is octane.
The compound on the right has an isopropyl group attached to the parent compound (heptane). Note
that all carbons in the molecules have four bonds.
CH3
CH2
CH2
CH3
CH
CH3
CH3 CH2 CH2 CH CH2 CH2 CH2 CH3
Propyl group attached to an 8-carbon chain
CH3 CH2 CH2 CH CH2 CH2 CH2 CH3
Isopropyl group attached to an 8-carbon chain
The carbon atoms on the end of the chain are called terminal carbons. When the bonding site of an alkyl
group occurs on a terminal carbon, the alkyl group is said to be "normal" and its name is sometimes
preceded by the letter n. Thus, the propyl group above could also be called n-propyl (pronounced
"normal propyl"). We will consider the use of this "n" prefix as optional. The other structure with the
bonding site on the center carbon is called isopropyl.
SECTION 25.4
IUPAC Rules for Naming Alkanes
A system for naming organic compounds has been developed by the International Union of Pure
and Applied Chemists (IUPAC). The system is accepted and used throughout the world. There is also a
method by which many organic compounds are given "common" names, but we will use only the IUPAC
system in this chapter. We will consider the rules one at a time and apply them to some practice problems.
RULE 1: Locate the longest continuous chain of carbon atoms. This will give you the name of the
"parent" compound.
For example, if the longest chain contains four carbons, the parent compound is butane. The longest
chains in the following two molecules are enclosed by a box:
CH3
CH2
CH2
CH3 CH2 CH CH2 CH2 CH
CH2
CH2
CH2
CH3
CH2
longest continuous chain = 11 carbons
CH3
CH3 CH CH2 CH CH2 CH2 CH3
CH2
CH3
CH2
CH3
longest continuous chain = 8 carbons
25-7 ©1997, A.J. Girondi

Problem 4. Draw a box around the longest continuous chain of carbon atoms in the structures below,
and name the parent compound for each one.
CH3
CH3
a. CH3 CH2 CH2 CH CH3 b. CH3 CH c. CH3 CH2 CH CH2
CH3
CH3
CH2 CH2 CH3
CH2
CH3
CH3
d. CH3 CH CH2 CH CH3
e. CH3 CH CH2 CH3
f.
CH3
C
CH2
CH3
CH2
CH3
CH2
CH3
CH2
CH3
a. parent: __________________________ d. parent: __________________________
b. parent: __________________________ e. parent: __________________________
c. parent: __________________________ f. parent: __________________________
RULE 2: The name of the parent compound is modified by noting what alkyl groups are attached to the
chain. Number the longest chain so that the alkyl group(s) will be on the lowest numbered carbons.
Note in the molecules shown below, that the longest chain should be numbered from right to left
in order to give the carbon which is bonded to the methyl group the lowest possible number:
1 2 3 4
CH3 CH2 CH CH3
CH3
Incorrect Numbering
4 3 2 1
CH3 CH2 CH CH3
CH3
Correct Numbering
The correct name of this compound is 2-methylbutane. The "2-" indicates that the methyl group is
attached to the second carbon in the longest chain. Note that the name of the alkyl group is added to that
of the parent compound (butane) to form one word, and that hyphens are used to separate numbers from
alphabetical parts of the name.
Problem 5. For the following compounds, draw a box around the longest continuous carbon chain and
name each molecule. The name of the molecule in part "b" is given to help you.
a. CH3 CH CH2 CH2 CH3
Name: ___________________________________
CH3
b. CH3 CH2 CH2 CH CH2 CH3 Name: __3-ethylhexane______________________
CH3
CH2
25-8 ©1997, A.J. Girondi

CH2
CH2
CH3
c.
CH3
CH2
CH2
CH2
CH
CH2
CH2
CH3
Name: ____________________________________
CH3
CH
CH3
d. CH3 CH2 CH2 CH CH2 CH2
CH2
CH2
CH3
Name: ____________________________________
RULE 3: When the same alkyl group occurs more than once in a molecule, the numbers of the carbons to
which they are attached are all included in the name. The number of the carbon is repeated as many times
as the group appears. The number of repeating alkyl groups is indicated in the name by the use of Greek
prefixes for 2, 3, 4, 5, etc. (di, tri, tetra, penta, etc.).
To better understand rule 3, study the following examples.
CH3
CH3 CH CH CH2 CH3
is called 2,3-dimethylpentane
CH3
Note that numbers used in the name are separated from each other by commas, and note that the
numbers are separated from the rest of the name with a hyphen.
CH2
CH3
CH3
CH2
CH2 C CH2 CH3
is called 3,3-diethylhexane
CH2
CH3
Problem 6. Name the four molecules whose structures are drawn below.
CH3
CH2
CH3
CH2
CH3
a. CH3 C CH3
b. CH3 C CH3
c.
CH3 CH2 CH2 CH2 C CH2 CH2 CH3
CH3
CH3
CH2
CH2
CH3
d.
CH3 CH CH2 CH2 CH3
CH3
CH
CH
CH3
CH3
a.
b.
c.
d.
25-9 ©1997, A.J. Girondi

RULE 4: If there are two or more different kinds of alkyl groups attached to the parent chain, name them in
alphabetical order.
For example:
CH3 CH CH CH2 CH3
CH3
CH2
CH3
is called 3-ethyl-2-methylpentane
It is NOT called 2-methyl-3-ethylpentane
However, when you are determining the alphabetical order, do not consider any Greek prefixes that are
being used. For example:
CH3 CH2 CH3
CH3 C CH2 CH CH2 CH2 CH3
CH3
is called 4-ethyl-2,2-dimethylheptane
It is NOT called 2,2-dimethyl-4-ethylheptane
Problem 7. Name the four molecules drawn below.
a.
CH3 CH2 CH2 CH CH2 CH CH2 CH2 CH3
CH3 CH2 CH3
CH3 CH2 CH2 CH3
b. CH3 CH2 C CH2 CH2 CH CH2 CH2 CH3
CH3
CH2
CH3
c. CH3 CH2 CH CH CH2 CH CH3
CH3
CH
CH3
CH3
CH3
CH3
d. CH3 CH CH2 CH CH2 CH2 CH CH3
CH2
CH3
RULE 5: To put the finishing touches on the name of an alkane, keep the following points in mind: (a)
hyphens are used to separate numbers from names of substituents; (b) numbers are separated from each
other by commas; (c) the last alkyl group to be named is prefixed to the name of the parent alkane, forming
one word; and (d) the suffix "-ane" indicates that the molecule is an alkane.
ACTIVITY 25.5
Using Molecular Models
The structure of alkanes is more understandable if you see them in three dimensions. We will use
molecular model kits for this purpose. Obtain a box containing a molecular model kit and determine which
parts represent carbon atoms, hydrogen atoms, carbon to carbon bonds, and carbon to hydrogen bonds.
When you have done this, assemble models of the six molecules drawn in Problem 4. Pick up one of your
25-10 ©1997, A.J. Girondi

models and rotate one section of the model while holding the other. Do you see how rotation is possible
around a single bond?_____________. Holding the model with both hands, bend and flex it a bit. Note
the bond angles between the carbons themselves and between the carbons and the hydrogens. Do you
see why these molecules are not really "straight" chains? ______________.
Because free rotation is possible around a single bond, what can you conclude about the 2 molecules
shown below? {1} ____________________________ If you named these two molecules, what would
you discover? {2} ________________________ What is the name? {3} ___________________________
CH3
CH3
CH
CH2 CH CH3
CH3
CH
CH2 CH CH3
CH3
CH3
CH3
SECTION 25.6
Cyclic Alkanes
The compounds we have studied so far have been either "straight" or "branched" chains. Carbon
atoms can also form rings which result in the formation of cyclic alkane molecules with the general formula,
CnH2n. Naming the cyclic alkanes is not difficult, but the rules do differ a bit from those used to name the
straight and branched chained compounds.
The name of a cyclic molecule requires the addition of the prefix "cyclo" to the name of the
hydrocarbon. Note the two condensed structural formulas below.
CH2
CH2
CH2
CH2
CH2
CH2
CH2
cyclopropane
cyclobutane
To make cyclic compounds easier to draw, a shorthand notation is used in which the hydrogens and
carbons which are part of the ring are not represented at all. The rings are represented by lines, and a
carbon atom is assumed to be present at each angle in the ring. The proper number of hydrogen atoms is
assumed to be attached to each carbon.
For example:
cyclopropane cyclobutane cyclopentane cyclohexane
C3H6 C4H8 C5H10 C6H12
Name this compound
{4}__________________________
25-11 ©1997, A.J. Girondi

Like the "straight-chained" compounds, cyclic molecules can also contain alkyl side chains. The
same general rules for alkane nomenclature apply to the cyclics, except that all positions in a ring are
equivalent, so a number is not needed to indicate the position of the alkyl group if there is only one alkyl
group on the ring. For example:
CH3
This is called methylcyclohexane
(It is NOT called 1-methylcyclohexane)
The carbon on which the alkyl group is located is automatically assumed to be number 1.
Problem 8. Name the cyclic molecules below.
CH3
CH2
CH2
CH3
CH2
CH2
CH3
a._____________________ b._____________________ c._____________________
If there are two or more substituents on a ring, numbers must be used to indicate their positions.
One of the substituents is always assigned position number 1, and starting at position 1, the chain is
numbered either clockwise or counterclockwise so as to give the other substituents on the ring the
smallest possible numbers. For example:
CH3
CH2
CH3
This is called 1-ethyl-2-methylcyclopentane
CH3
CH3
This is called 1,2-dimethylcyclopentane
(It is NOT called 1,5-dimethylcyclopentane)
CH3
CH2
CH3
This is called 1-ethyl-4-methylcyclohexane
(You may have wanted to call it 4-ethyl-1-methylcyclohexane,
but we chose to assign the number 1 position to ethyl since it
comes first, alphabetically, and since we get the same
numbers,1 and 4, either way.)
CH3
CH2
CH3
This is called 4-ethyl-1,2-dimethylcyclopentane
CH3
25-12 ©1997, A.J. Girondi

In the last example, we assign position 1 to the carbon in the lower right corner and number the ring
counterclockwise. This gives the lowest possible set of numbers for the three substitutents on the ring.
CH3
CH2
CH3
This is called 3-ethyl-1,1,2-trimethylcyclobutane
CH3
CH3
(We numbered clockwise this time)
In the molecule drawn above, if we assigned position #1 to the carbon which is bonded to the ethyl group,
we would have had to number counterclockwise and name the molecule: 1-ethyl-2,3,3-trimethylbutane.
This was avoided because it resulted in higher numbers.
The three structures drawn below are identical. Write the name: {5} _____________________________
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
Problem 9. Name the cyclic alkanes shown below:
a.
CH3
CH2
CH2
CH3
CH3
b.
CH3
CH3
c.
CH3
CH2
CH3
CH3
d. CH2 CH3
CH2
CH3
CH3
e. CH3
CH3
CH
f. g. CH2 CH2 CH3
CH3
CH3
CH3
CH3
a. __________________________________ e. __________________________________
b. __________________________________ f. __________________________________
c. __________________________________ g. __________________________________
d. __________________________________
25-13 ©1997, A.J. Girondi

ACTIVITY 25.7
Models of Cyclic Alkanes
Using a molecular model kit, construct the four cyclic molecules drawn below. The models give
you some idea of what these cyclic compounds look like in three dimensions. You will also see the effects
of the bond angles on the shapes of the molecules. Be sure to include all needed hydrogen atoms, even
if they are not shown on the drawings.
cyclopropane cyclobutane cyclopentane cyclohexane
C3H6 C4H8 C5H10 C6H12
Do any of these cyclic compounds have what you might consider to be flat rings? If so, which one(s)?
{6}____________________________________________________________________________
Here is a summary of the rules used to name alkanes:
RULE 1: Locate the longest continuous chain of carbon atoms. This will give you the name of the
"parent" compound.
RULE 2: The name of the parent compound is modified by noting what alkyl groups are attached to the
chain. Number the longest chain so that the alkyl group(s) will be on the lowest numbered carbons.
RULE 3: When the same alkyl group occurs more than once in a molecule, the numbers of the carbons to
which they are attached are all included in the name. The number of the carbon is repeated as many times
as the group appears. The number of repeating alkyl groups is indicated in the name by the use of Greek
prefixes for 2, 3, 4, 5, etc. (di, tri, tetra, penta, etc.).
RULE 4: If there are two or more different kinds of alkyl groups attached to the parent chain, name them in
alphabetical order.
RULE 5: The put the finishing touches on the name of an alkane, keep the following points in mind: (a)
hyphens are used to separate numbers from names of substitutents; (b) numbers are separated from
each other by commas; (c) the last alkyl group to be named is prefixed to the name of the parent alkane,
forming one word; and (d) the suffix "-ane" indicates that the molecule is an alkane.
SECTION 25.8
Naming Alkenes
Now that you are an expert on alkanes, let's take a look at the alkene functional group. A
functional group is a feature of a class of compounds that is responsible for its characteristic properties.
The functional group of the alkanes is the single bond. The functional group of the alkenes is the double
bond. Alkenes contain at least one double bond which exists between a pair of carbon atoms. The
general formula for the straight-chained alkenes is CnH2n. The suffix to be used in the names of alkenes is
"-ene." The rules for naming alkenes are the same as those for alkanes with a few additional restrictions.
25-14 ©1997, A.J. Girondi

Additional Rules for the Nomenclature of Alkenes:
RULE 1: The chain chosen as the parent chain must contain the carbon–carbon double bond (C=C).
RULE 2: The parent chain must be numbered to give the carbon-carbon double bond the lowest possible
number.
RULE 3: The name of the alkene must contain a number to indicate the position of the double bond.
Note the example below. The longest carbon chain alkene is numbered correctly, giving the double bond
the lowest possible number.
2
1
CH2
7 6 5 4
CH3
As we number the carbons, the first carbon involved in the
CH3 CH2 CH CH C CH3 double bond is #3, so the parent chain is called 3-heptene.
CH3
3
Methyl groups are located on carbons #3 and #5.
3,5-dimethyl-3-heptene
A number is not used to locate the double bond in chains which are shorter than four carbons. Two
examples are below.
CH2 CH2 This is called ethene, not 1-ethene
CH3
CH
CH2
This is called propene, not 1-propene
Why is it that these two molecules do not require the use of the number? {7} ______________________
______________________________________________________________________________
Problem 10. Name the alkenes below. After you have located the longest chain containing the double
bond, be sure to number the chain so that the double bond gets the lowest possible number.
a. CH3 – CH2 – CH = CH2 ___________________________________________________________
b. CH3 – CH = CH – CH3 ___________________________________________________________
c. CH3 – CH2 – CH = CH – CH3 ___________________________________________________________
d. CH3 – CH2 – CH = CH – CH2 – CH3 ___________________________________________________________
e. CH2 = CH2 ___________________________________________________________
f. CH3 – CH = CH2 ___________________________________________________________
CH3
g.
CH3
CH
CH2 CH CH
CH2
CH3
25-15 ©1997, A.J. Girondi

h.
CH3
C
CH
CH3
CH2
CH3
i. CH3 CH CH CH2
CH3
CH2 CH3
j. CH3 CH CH C CH2 CH3
CH2
CH3
SECTION 25.9 Naming Cycloalkenes
Cycloalkenes are named similarly to straight chained alkenes. The carbons in the ring that contain
the double bond are always assigned the #1 and #2 positions, so numbers are used only to locate the
positions of substitutents attached to the ring - not to locate the position of the double bond. The general
formula for cyclic alkenes in CnH2n-2. Study the examples below.
CH3
CH3
cyclobutene 3-methylcyclohexene 3,4-dimethylcyclopentene
CH3
Problem 11. Name the following cycloalkenes.
a. CH2 CH3
CH3
b.
CH3
CH3
CH2
CH3
c.
CH3
25-16 ©1997, A.J. Girondi

CH3
CH
CH3
d.
CH2 CH2 CH3
e.
CH3
CH3
f.
CH2
CH3
CH2 CH2 CH2 CH3
SECTION 25.10
Naming Alkynes
The functional group of the compounds known as the alkynes is a triple bond. The general
formula for straight-chained alkynes is CnH2n-2. Alkynes are named in much the same way as the alkenes,
except that their names end with the suffix "-yne", signifying the triple bond. Once again, the triple bond
must be located within the parent chain, and it should be assigned the lowest possible number.
Additional Rules for the Nomenclature of Alkynes:
RULE 1: The chain chosen as the parent chain must contain the carbon- carbon triple bond.
RULE 2: The parent chain must be numbered to give the carbon-carbon triple bond the lowest possible
number.
RULE 3: The name of the alkyne must contain a number to indicate the position of the triple bond.
As was the case with the alkenes, no number is used to locate the triple bond if the parent chain is shorter
than four carbons:
CH
CH
CH C CH3
CH C CH2 CH3
CH3
C
C
CH3
ethyne
propyne
1-butyne
2-butyne
For the example at right, the correct name is 5-methyl-2-hexyne
1 2 3 4 5 6
CH3 C C CH2 C CH3
CH3
25-17 ©1997, A.J. Girondi

Problem 12. Name the alkynes drawn below. Be sure to number the parent chain so as to give the
triple bond the lowest possible number.
a. CH C – CH2 – CH2 – CH3 __________________________________________
b. CH3 – CH2 – CH2 – C C – CH3 __________________________________________
c. CH3 – CH2 – C C – CH3 __________________________________________
d. CH3 – CH2 – CH2 – C CH __________________________________________
e. CH3 – C C – CH2 – CH2 – CH2 – CH3 _______________________________________________________________
f. CH3 CH C CH
CH3
CH3
g. CH3 CH2 CH CH C CH
CH2
CH3
CH3
h.
CH C C CH3
CH2
CH2
CH3
i. CH3 C C CH CH2
CH3
CH
CH3
CH2
CH2
CH3
Table 25.1
Summary of General Formulas for
Alkanes, Alkenes, and Alkynes
Class of Compound General Formula
Straight-chained alkanes
Cycloalkanes
Alkenes
Cycloalkenes
Alkynes
CnH2n+2
CnH2n
CnH2n
CnH2n-2
CnH2n-2
25-18 ©1997, A.J. Girondi

SECTION 25.11
Review Problems
Problem 13. The names of the compounds listed below are NOT correct. Using the incorrect name,
draw the structural formula in the work area. Then write the correct name of each compound on the line
provided.
Incorrect Name Correct Name Work Area
a. 4,4-dimethylhexane ___________________________
b. 2-n-propylpentane ___________________________
c. 1,1-diethylbutane ___________________________
d. 1,4-dimethylcyclobutane ___________________________
e. 3-methyl-2-butene ___________________________
f. 5-ethylcyclopentene ___________________________
g. 2-n-propyl-1-propene ___________________________
h. 2-isopropyl-3-heptene ___________________________
i. 2,2-dimethyl-3-butyne ___________________________
j. 5-octyne ___________________________
25-19 ©1997, A.J. Girondi

Problem 14. Write condensed structural formulas for the following:
Name
Condensed Structural Formula
a. 4-isopropyloctane
b. 3,4-dimethyl-4-n-propylheptane
c. 1,1-dimethylcyclobutane
d. 3-ethyl-3-heptene
e. 3-ethyl-2-methyl-1-hexene
f. 3-octene
g. 3,3-dimethyl-1-butyne
h. 4,4-dimethyl-2-pentyne
i. 3-n-butyl-2-ethylcyclohexene
j. 3,4-diethyl-4,6-dimethylnonane
25-20 ©1997, A.J. Girondi

SECTION 25.12
Learning Outcomes
Before leaving this chapter, read through the learning outcomes listed below. Place a check
before each outcome when you feel you have mastered it. When you have completed this task, arrange
to take any quizzes or exams on this chapter, and move on to Chapter 26.
_____1. Distinguish between organic and inorganic compounds.
_____2. Distinguish between alkanes, alkenes, and alkynes.
_____3. Determine the number of carbon atoms in the longest chain of any alkane, alkene, or alkyne.
_____4. Use the IUPAC system to name alkanes, alkenes, and alkynes, given their condensed structural
formulas.
_____5. Given the IUPAC names, be able to draw condensed structural formulas for alkanes, alkenes,
and alkynes.
25-21 ©1997, A.J. Girondi

SECTION 25.14 Student Notes
25-26 ©1997, A.J. Girondi

NAME________________________________ PER ________ DATE DUE ___________________
ACTIVE LEARNING IN CHEMISTRY EDUCATION
CHAPTER 26
INTRODUCTION
TO ORGANIC
COMPOUNDS
(Part 2)
26–1 ©1997, A.J. Girondi

NOTICE OF RIGHTS
All rights reserved. No part of this document may be reproduced or transmitted in any form by any means,
electronic, mechanical, photocopying, or otherwise, without the prior written permission of the author.
Copies of this document may be made free of charge for use in public or nonprofit private educational
institutions provided that permission is obtained from the author . Please indicate the name and address
of the institution where use is anticipated.
© 1997 A.J. Girondi, Ph.D.
505 Latshmere Drive
Harrisburg, PA 17109
alicechem@geocities.com
Website: www.geocities.com/Athens/Oracle/2041
26–2 ©1997, A.J. Girondi

SECTION 26.1
Alcohols
Alcohols are molecules in which an alkyl group is attached to a hydroxy group (–OH). The
hydroxy group is responsible for the characteristic properties of alcohols so we refer to it as the functional
group for alcohols. There are three different methods for naming alcohols, but we will use only the IUPAC
system. The rules that you used for naming alkanes and alkenes (in Chapter 25) are similar to those used
for the alcohols. The modified rules are listed below.
Additional Rules for the Nomenclature of Alcohols:
RULE 1:
RULE 2:
RULE 3:
RULE 4:
Locate the longest continuous chain of carbon atoms which contains the "hydroxy" (–OH)
group. This chain will serve to identify the parent compound.
Number the chain so as to give the carbon atom which is bonded to the –OH group the lowest
possible number.
A number is included before the name of the parent compound to indicate the position of the
–OH group.
The suffix "ol" is added to the name to indicate that the molecule is an alcohol.
Study the examples below. Note that the number indicating the position of the –OH group is not used if
the chain is shorter than 3 carbons. Why? {1} _____________________________________________
______________________________________________________________________________
Name Formula Condensed Structural Formula
methanol
CH3OH
CH3
OH
ethanol
CH3CH2OH
CH3
CH2
OH
1–propanol
CH3CH2CH2OH
CH3
CH2
CH2
OH
OH
2–propanol
CH3CHOHCH3
CH3
CH
CH3
H
H
cyclopentanol
H
H
C
C
C
H
OH
OH
H
C C
H H
H
26–3 ©1997, A.J. Girondi

In addition, you see in the example above that the position of the –OH ("hydroxy") group is not included in
the names of cyclic alcohols, either. Why not? (Remember that this is also the case for the double bond
in cyclic alkenes. {2} ________________________________________________________________
(The hydroxy group,–OH, should not be confused with the hydroxide ion, OH 1– . The hydroxy group has
the same formula, but it is not an ion.)
Problem 1. Name the alcohols given below.
a. CH3–CH2–CH–CH2–CH3
OH
b. CH3–CH–CH2–CH3
OH
c. CH3–CH–CH–CH3
OH
CH3
OH
CH3
d. CH3–CH–CH2–CH–CH–CH3
CH3
e. CH3–CH2–CH–CH2–CH2–CH2–OH
CH2
CH3
f.
OH
g.
OH
CH3
h. CH3 OH
CH3
i.
CH3
OH
CH2
CH3
26–4 ©1997, A.J. Girondi

OH
j. CH3–CH–CH3
This compound is commonly called "rubbing
alcohol." Give its IUPAC name.
Problem 2. Draw the condensed structural formulas for the following.
a. 4,4–dimethyl–2–hexanol b. cyclopropanol
c. 2,3–diethylcyclohexanol d. 3,4–diethyl–2–heptanol
Section 26.2
Ethers
Ethers are compounds which contain an oxygen atom bonded to two carbon atoms within the
carbon chain. The functional group is the C–O–C arrangement found within the chain. When you look at
an ether molecule, you will see an alkyl group on each side of the oxygen. For example,
CH3–CH2–O–CH3 has an ethyl group on the left of the oxygen atom and a methyl group on the right. The
"common name" for this molecule is methyl ethyl ether. Although common names are still frequently used
for ethers, we will stick to our "game plan" and use the IUPAC system.
Parent compound is "ethyl"
CH 3 –CH 2 –O–CH 3
Functional group is "methoxy"
In the IUPAC system, the larger of the two alkyl groups attached to the oxygen is considered to be
the parent compound. For the ether mentioned in the last paragraph above, the parent compound would
be ethane. The smaller alkyl group and the oxygen atom are considered to be a substituent group on the
parent compound. The –O–CH3 group is the substituent and it is called "methoxy." So the name of that
ether is methoxyethane. If the substituent had been CH3–CH2–O–, it would have been called "ethoxy."
Collectively these functional groups of the ethers are known as alkoxy groups. Only one modified rule
needs to be mentioned here regarding the nomenclature of ethers.
26–5 ©1997, A.J. Girondi

Additional Rule for the Nomenclature of Ethers:
RULE: For ethers with parent chains that contain 3 or more carbon atoms, a number is included to
indicate the position of the alkoxy group.
Study the examples below.
CH3–O–CH3 CH3–CH2–O–CH2–CH3 CH3–O–CH2–CH2–CH3 CH3–O–CH–CH3
methoxymethane ethoxyethane 1–methoxypropane 2–methoxypropane
CH3
Problem 3. Name the following ethers:
a. CH3–O–CH2–CH2–CH2–CH3 ___________________________________
b. CH3–CH2–CH2–O–CH2–CH2–CH3 ___________________________________
c. CH3–CH2–O–CH–CH2–CH2–CH3 _____________________________________________________
CH3
Draw condensed structures for the following ethers:
d. methoxycyclohexane e. 3–methoxycyclopentene
f. 4–ethoxynonane g. 2–isopropoxybutane
Section 26.3 Aldehydes and Ketones
The next two organic functional groups we will study are those of the aldehydes and ketones.
Aldehydes and ketones contain a carbonyl group, which consists of an oxygen atom which is
double–bonded to a carbon atom. There are two kinds of carbonyl groups involved here. In aldehydes, at
least one hydrogen is attached to the carbonyl carbon, while in ketones, two carbon atoms are always
attached to the carbonyl carbon.
O
O
O
C
C
H
C
C
C
carbonyl group aldehyde group ketone group
26–6 ©1997, A.J. Girondi

It is helpful to note that in an aldehyde the carbonyl carbon is always a terminal carbon, which means it
always occurs at one end of the carbon chain. In ketones, the carbonyl carbon is never a terminal carbon.
The nomenclature of aldehydes requires a few rule modifications:
Additional Rules for the Nomenclature of Aldehydes:
RULE 1: The longest continuous chain containing the aldehyde group is considered to be the parent
compound.
RULE 2: The carbonyl carbon is part of the parent chain and is always considered to be in the #1 position.
RULE 3: The suffix "al" is added to the name of the parent compound to indicate that the compound is an
aldehyde.
Note the examples of aldehydes shown below. You see that no number is needed to indicate the
position of the functional group since it is always at position #1.
CH3–CH2
H
C O
CH3
CH3–CH–CH2–CH2
H
C O
propanal
4–methylpentanal
H
O
C
CH2–CH3 CH3
CH2–CH2–CH2–CH–CH2–CH2–CH–CH2–CH3
5–ethyl–8–methyldecanal
The nomenclature of ketones also requires a few rule modifications.
Additional Rules for the Nomenclature of Ketones:
RULE 1: The longest continuous chain containing the ketone group is considered to be the parent
compound.
RULE 2: A number is included before the name of the parent compound to indicate the position of the
ketone group. The chain is always numbered so that the carbonyl carbon has the lowest
possible number.
RULE 3: The suffix "one" is added to the name of the parent compound to indicate that the compound is
a ketone.
For example:
O
O
CH3
C
CH3
CH3 CH2 C CH2 CH3–CH–CH2–CH2–CH2–C O
CH3
CH3
CH3
2–propanone 3–pentanone 6–methyl–2–heptanone
26–7 ©1997, A.J. Girondi

Why would it be impossible for a ketone to have a name like 3–methyl–1–hexanone? {3} _____________
_____________________________________________________________________________
Problem 4. Name the molecules shown below.
O
a.
CH3
CH2
C
CH3
O
b.
CH3
CH
CH2
C
H
CH3
CH3
c.
d.
CH3–CH2–CH–CH–CH3
C O
H
CH3 CH2–CH3
CH3–CH–CH–CH2– C O
CH3
e.
CH3–CH2–CH2
C
O
CH3
CH2–CH2–CH–CH3
Section 26.4 Organic Acids
Organic acids are molecules that contain a carboxyl group (sometimes called a carboxylic acid
group). This functional group consists of a carbon which is doubled bonded to an oxygen atom, as was
the case with aldehydes and ketones. However, in an acid a hydroxy group (–OH) is also bonded to that
same carbon. Be careful not to confuse organic acids with alcohols, aldehydes, or ketones. As was the
case with aldehydes, this functional group always occurs on a terminal carbon of the parent chain.
Therefore, a number is not used in the name to locate the carboxyl group.
Additional Rules for the Nomenclature of Carboxylic Acids:
RULE 1: The longest continuous chain containing the carboxyl group is considered to be the parent
compound.
RULE 2: The carboxyl carbon is part of the parent chain and is always considered to be in the #1 position.
RULE 3: The suffix "oic" is added to the name of the parent compound, and the word "acid" is added to
the name.
26–8 ©1997, A.J. Girondi

For example:
O
O
CH3
O
H
C
CH3 C
CH3–CH–CH2–CH2 C
OH
OH
OH
methanoic acid ethanoic acid 4–methylpentanoic acid
Acids also have common names. For example, ethanoic acid is also called acetic acid or "vinegar." We will
work only with the IUPAC names.
As you attempt to name the carboxylic acids, note that the carboxyl group is written in shorthand as
–COOH in the condensed structural formulas.
Problem 5. Name the organic acids below.
a. CH3–CH2–CH–CH2–CH2–COOH __________________________________
CH2 – CH3
b. CH3–CH2–CH2–CH2–CH2–COOH __________________________________
c.
d.
CH3–CH2–CH2
CH3–CH2–CH–CH2–COOH
CH3–CH–CH2–CH2–CH–CH2–CH2–COOH
CH3 CH3
__________________________________
__________________________________
e.
CH3
__________________________________
CH–CH2–COOH
CH3
CH2–CH2–CH2–CH3
f. CH3–C–CH2–CH2–COOH
__________________________________
CH2–CH2–CH2–CH3
Section 26.5 Esters
Esters are organic compounds which are very common in nature. For
example, fats and oils are esters. Esters are also responsible for many of the odors
and flavors of fruits. Oil of wintergreen and aspirin are esters. Esters can be
considered to be derivatives of carboxylic acids. The functional group of esters looks
similar to the carboxyl group of acids, except that the hydrogen atom on the hydroxy
group is replaced with an organic group such as an alkyl group. The letter "R" in the
structure at right represents some organic group (methyl, ethyl, etc.).
C
O
O
R
26–9 ©1997, A.J. Girondi

O
O
O
C
C
C
O H
O R
O CH3
carboxyl group general ester group sample ester group
Esters are named by first naming the "R" group followed by the name of the acid portion. The suffix of the
acid derivative is then changed from "–ic" to "–ate." For example, in the leftmost structure below, the
parent acid is ethanoic acid. The "R" group is methyl, so the name of the ester is methyl ethanoate. In the
center structure, the parent acid is butanoic, while the "R" group is ethyl, so the ester is named ethyl
butanoate. Notice that the names of esters consist of two words, while the names of most of the previous
types of compounds you have studied consisted of only one word.
CH3 – C
O
O– CH3
CH3 – CH2 – CH2 – C
O
O– CH2 – CH3
H – C
O
O– CH2 – CH3
methyl ethanoate ethyl butanoate ethyl methanoate
(pineapples) (artificial rum flavor)
Artificial flavors of strawberry, apple, raspberry, cherry, etc., are made from esters.
Additional Rules for the Nomenclature of Esters:
RULE 1: Determine the name of the "R" group.
RULE 2: Place the name of the "R" group in front of the name of the parent acid, forming two words.
RULE 3: Determine the name of the parent acid, and change its suffix from "–ic" to "–ate." Drop the word
"acid."
Problem 6. Name the esters below.
O
a. CH3 – CH2 – CH2 – C
b. CH3 – CH2 – CH2 – CH2 – C
O – CH2 – CH2 – CH3
O
O– CH3
O
c. CH3 – CH2 – C
d. CH3 – C
O – CH2 – CH2 – CH2 – CH3
O
O– CH – CH3
CH3
26–10 ©1997, A.J. Girondi

O
e. CH3 – CH2 – CH2 – CH2 – C
f. H – C
O– CH2 – CH2 – CH3
O
O– CH2 – CH2 – CH2 – CH2 – CH3
Section 26.6
Amines
Amines are organic compounds which are related to ammonia (NH3). All amines have the element
nitrogen in them. There are three basic kinds of amines:
1. In primary amines one hydrogen atom in ammonia has been replaced by an alkyl group.
2. In secondary amines two hydrogen atoms in ammonia have been replaced by two alkyl groups.
3. In tertiary amines all three hydrogen atoms in ammonia have been replaced by three alkyl
groups. Examine the examples below:
H
H
CH3
CH
CH3
CH3 N H
CH3 CH2 N
CH2 CH3 CH3 N CH2 CH3
A Primary Amine A Secondary Amine A Tertiary Amine
According to the IUPAC system, primary amines are named by treating the –NH2 (amino) group in
the molecule as a substituent group on the longest (parent) chain of carbon atoms. For example, the
primary amine shown above is called aminomethane. Two more examples are shown below.
CH3 – CH2 – CH – CH2 – CH2 – CH3
CH3
NH2
H
N
H
CH3 – CH – CH2 – CH – CH2 – CH2 – CH3
3–aminohexane 4–amino–2–methylheptane
(a primary amine) (a primary amine)
Secondary and tertiary amines are named according to a "common" naming system. Primary
amines can have either IUPAC or common names. Amines are the only organic compounds for which we
will learn common names. In the common system, amines are named by adding the names of the alkyl
group(s) attached to the nitrogen atom to the word "amine." In the past, the alkyl groups were named in
order of size (smallest first) instead of in alphabetical order is normally done in the IUPAC system.
However, today we follow the IUPAC rules and name the alkyl groups in alphabetical order. For example,
the name of the secondary amine shown above is diethylamine. The name of the tertiary amine above is
ethylisopropylmethylamine. Study the examples below. Note that the primary amine can have two names.
26–11 ©1997, A.J. Girondi

CH3
CH2
CH2
CH3
CH2 CH2 CH2 CH2
CH3
CH3 N CH3
H
N
CH3
trimethylamine methylpropylamine pentylamine (common)
1–aminopentane (IUPAC)
a tertiary amine a secondary amine a primary amine
H
N
H
Additional Rules for the Nomenclature of Amines:
RULE 1: In primary amines only, the IUPAC system treats the NH2 (amino) group as a substituent group
on the parent chain.
RULE 2: When using the common naming system, the names of the alkyl groups which are attached to
the nitrogen atom are listed in alphabetical order and are attached to the suffix "amine" to
form one word. Greek prefixes are used if specific alkyl groups occur more than once in a
molecule. Name the amines below. Where two lines are present, give two names.
Problem 7. Name the amines below. Where two lines are present, give two names.
a.
CH3
CH3 N CH2 CH3
b.
H
CH3 N CH2 CH3
c. CH3 – CH2 – CH2 – CH – CH2 – CH – CH3
CH3
NH2
d.
CH3 CH2 CH2 CH2
CH2
H
N
CH3
e.
CH2
CH3
CH3 CH2 N CH2 CH3
f.
CH2
CH3
CH3 – CH – CH2 – CH2 – CH2 – CH2 – CH2 – NH2
g.
CH3
NH2
CH
CH3
26–12 ©1997, A.J. Girondi

h.
NH2
Section 26.7
Amides
You are already familiar with the carboxyl group which is the functional group of a carboxylic acid. If
you replace the hydroxy group (–OH) in the carboxyl group with an amino group (–NH2), you get the
functional group of a class of organic compounds known as primary amides.
O
C
O H
carboxyl group
O
C
NH2
amide group
There are three classes of amides just as there were for amines, but we will consider only primary
amides, and we will name them according to the IUPAC system. Amides are considered to be derivatives
of carboxylic acids, which means they are formed from acids. Thus, the amides are named as derivatives of
acids. To name an amide, simply identify the name of the organic acid from which the amide was derived,
and change the "–oic" suffix in the acid's name to "–amide." The examples of amides shown below were
derived from ethanoic, propanoic, and butanoic acids.
O
O
CH3
O
CH3
C
CH3
CH2
C
CH3
CH
CH2
C
NH2
NH2
NH2
ethanamide propanamide 3–methylbutanamide
Additional Rules for the Nomenclature of Amides:
RULE 1:
RULE 2:
Identify the carboxylic acid from which the amide was derived and change the suffix of the acid
name from "–oic" to "–amide," and drop the word acid.
Add the names of any alkyl groups to the name of the parent compound, forming one word.
Problem 8. Name the amides shown below. Note that the amide functional group is written in
shorthand as CONH2.
a. HCONH2 b. CH3–CH2–CH2–CH2–CONH2
__________________________________
____________________________________
26–13 ©1997, A.J. Girondi

CH3
c. CH2–CH3
d.
CH3–CH2–CH–CH2–CH2–COHN2
CH3–C–CH2–CONH2
CH3
__________________________________
____________________________________
e. CH2–CH3
f.
CH3
CH3
CH3–CH2–CH–CH2–CH–CH2–CONH2
CH3
__________________________________
CH3–CH–CH2–C–CH2–CONH2
CH3
____________________________________
Section 26.8
Halogenated Hydrocarbons
The last group of compounds we are going to discuss includes some that are of great importance
and interest today. Included are the chlorofluorocarbons that are used in refrigeration and air conditioning
systems and which are thought to be involved in the depletion of ozone in the upper atmosphere.
This class of organic compounds is known as the halogenated hydrocarbons. In addition to their
use in refrigerants they are used as solvents, aerosol sprays, antiseptics, dry cleaning fluids, insecticides,
herbicides, and anesthetics. Most of these compounds are synthetic (human– made).
In these compounds, the functional group is a single atom of a halogen such as fluorine, chlorine,
bromine, or iodine. In the IUPAC system, the halogen atoms are considered to be substituents on the
parent chain. The "–ine" suffix of the halogen's name is dropped and the letter "o" is added before being
added to the name of the parent compound. For example, fluorine becomes "fluoro," chlorine becomes
"chloro", bromine becomes "bromo," and iodine becomes "iodo." Note the examples below.
H
H H
H H
H
H F
H
H I
H H H
H–C–I
H–C–C–Cl
H–C–C–C–Br
H–C–C–C–C–C–C–C–C–H
H
H
H
H
H
H
H
H
H
F
H H H H
iodomethane chloromethane 1–bromopropane 2,4–difluoro–5–iodooctane
CH3–I CH3–CH2–Cl CH3–CH2–CH2–Br CH3–CHF–CH2–CHF–CHI–CH2–CH2–CH3
Numbers are not used to indicate the position of a single halogen atom substituent unless the parent
carbon chain is longer than 2 atoms; however, if more than one halogen atom substituent is present, then
numbers are needed on a two–carbon chain, too! Study the following examples.
H Cl
H–C–C–Cl
H H
Cl–C–C–Cl
Br
H–C–H
H H
H H
F
1,1–dichloroethane 1,2–dichloroethane bromofluoromethane
26–14 ©1997, A.J. Girondi

Additional Rules for the Nomenclature of Halogenated Hydrocarbons:
RULE 1:
RULE 2:
Drop the "–ine" suffix from the name of the halogen atom(s) and add a suffix consisting of the
letter "o".
Add the altered name(s) of the halogen atom(s) to that of the parent compound.
Problem 9. Name the halogenated compounds below.
Cl
a. CH3 – CH2 – CH – CH – CH3
Cl
H
b. F – C – F
H
I
c. CH3 – CH – CH – CH – CH2 – CH3
F
Br
Br
d. CH3 – CH – CH = CH2
e. CH2 – CH2 – CH2 – Br
CH2 – CH2 – CH2 – CH3
F
f. Cl – C – Cl
F
Problem 10. Write condensed structural formulas (such as those shown above) for the following.
a. tetrafluoromethane
b. 1,1,1–trichloroethane
26–15 ©1997, A.J. Girondi

c. chlorocyclopentane
d. 1,3–difluoro–2–iodocyclohexane
e. 3,4–dibromo–6–methyl–1–heptyne
f. 3–chlorocyclopentene
g. 2,3–dichlorocyclobutene
Section 26.9 A Review of Organic Nomenclature
The remainder of this chapter consists of a review of nomenclature of the various classes of
organic compounds which you have studied.
Problem 11. Some of the names of the six compounds listed below are incorrect. If the name is
correct, respond with "O.K." If the name is incorrect, provide the correct name.
a. 3–chloropentane ___________________________________
b. 1,1–dimethyl–1–propanol ___________________________________
c. 2,2,3–trimethyl–4–bromoheptane ___________________________________
d. 4–methyl–4–hexanol ___________________________________
e. 2,2–dimethyl–3–chloro–3–butanol ___________________________________
f. 1–ethyl–2–ethanol ___________________________________
26–16 ©1997, A.J. Girondi

Problem 12. Draw condensed structural formulas for the compounds named below.
a. 1,3,5–tribromocyclohexane b. 2,3–dichlorobutane
c. 2–ethyl–3–methyl–1–pentanol d. 1–ethoxypropane
e. 2–iodo–3–isopropylcyclohexanol f. 3,3–dimethylbutanal
g. 2–methoxy–3–heptanone h. 3–pentanone
i. 3,4–diethylhexanal j. 2,4–difluorohexanoic acid
k. 2–hydroxybutanoic acid l. ethyl ethanoate
m. n–propyl octanoate n. 4–bromo–3–chloroheptane
26–17 ©1997, A.J. Girondi

o. ethylmethylamine p. isopropyldimethylamine
q. propanamide r. 3–methylbutanamide
s. 4–chloro–2–pentanone t. 2,3,4–triiodopentanoic acid
Problem 13. Give another name for each of the following:
a. ethylamine _____________________________________________
b. isopropylamine _____________________________________________
Section 26.11 Learning Outcomes
Before leaving this chapter, read through the learning outcomes listed below. Place a check
before each outcome when you feel you have mastered it. When you have completed this task, arrange
to take any quizzes or exams on this chapter.
_____1. Given their names or condensed structural formulas, distinguish between alcohols, ethers,
aldehydes, ketones, organic acids, esters, amines, amides, and halogenated compounds.
_____2. Given their names, draw condensed structural formulas for the classes of compounds given in
outcome 1 above.
_____3. Given their condensed structural formulas, give the IUPAC names of molecules belonging to
the classes of compounds listed in outcome 1 above.
_____4. Given their condensed structural formulas, give the common names of secondary and tertiary
amines.
26–18 ©1997, A.J. Girondi

NAME________________________________ PER ________ DATE DUE ___________________
ACTIVE LEARNING IN CHEMISTRY EDUCATION
CHAPTER 28
NUCLEAR
CHEMISTRY
(Part 1)
28-1 ©1997, A.J. Girondi

NOTICE OF RIGHTS
All rights reserved. No part of this document may be reproduced or transmitted in any form by any means,
electronic, mechanical, photocopying, or otherwise, without the prior written permission of the author.
Copies of this document may be made free of charge for use in public or nonprofit private educational
institutions provided that permission is obtained from the author . Please indicate the name and address
of the institution where use is anticipated.
© 1997 A.J. Girondi, Ph.D.
505 Latshmere Drive
Harrisburg, PA 17109
alicechem@geocities.com
Website: www.geocities.com/Athens/Oracle/2041
28-2 ©1997, A.J. Girondi

SECTION 28.1
Nuclear Notation and Isotopes
Nuclear chemistry involves changes that occur in the nucleus of an atom. These changes in a
nucleus often result in the release of great amounts of energy – much greater than the amount of energy
released in any chemical reactions. You will recall that chemical reactions involve the formation and
breaking of bonds between atoms. In addition to the release of energy, certain types of particles are
emitted from a nucleus during nuclear reactions. Before going on, there are a few basic facts which you
should know:
1. Most of the mass of an atom is found in the nucleus. This is a result of the relatively close
"packing" of the protons and neutrons in it.
2. All protons carry a positive charge.
3. Because they all carry a positive charge, the protons in a nucleus repel each other with a strong
force; yet, the nucleus of a stable atom does not fall apart.
You may recall that it is the number of protons in the nucleus of an atom (the atomic number) that
determines what element the nucleus represents. A nuclear change sometimes involves a change in the
number of protons in the nucleus. When this happens, a nucleus of one element is changed into a
nucleus of a different element. This is called a transmutation. In a previous chapter, you were
introduced to nuclear notation. Let's review it now to refresh your memory. The general form for nuclear
notation can be represented by the expression shown below:
mass number
(sum of protons
and neutrons)
atomic number
(number of protons)
A
Z
X
symbol of the element
What would the expression A minus Z, or A - Z, represent? {1} _________________________________
If the value of Z changes, will X change? {2} _______________ If Z changes by a value of 2, what will
happen to the value of A? {3} _________________________________________________________
You learned previously that atoms of an element can exist in different forms known as isotopes.
Isotopes are atoms of an element that contain different numbers of neutrons. Therefore, isotopes have
different masses and different mass numbers – although they have the same atomic number. Some
elements have many isotopes, while others have only a few. In addition, some isotopes of elements are
naturally-occurring while others are man-made. Some isotopes are unstable, meaning that they
decompose or break apart on their own. Many elements possess both stable and unstable isotopes.
Unstable isotopes are said to be radioactive. They give off energy and/or nuclear particles when they
decompose. In Table 28.1, the mass numbers of isotopes of some selected elements are shown.
If ALL of the isotopes of an element happen to be radioactive, then the element itself is
categorized as being radioactive. With this in mind, which of the selected elements listed in Table 28.1
should be categorized as radioactive? {4}____________________________ How many radioactive isotopes does
carbon (C) have? {5} _________ How many nonradioactive isotopes does nitrogen (N) have?
{6}_________ How many man-made radioactive isotopes does helium (He) have? {7} _________ All
elements on the periodic table with an atomic number of 84 or greater are radioactive. These elements are
shown as they occur on the periodic table in Table 28.2.
28-3 ©1997, A.J. Girondi

Table 28.1
Isotopes of Some Selected Elements
In this table, mass numbers of naturally-occurring nonradioactive isotopes are given in plain type; mass
numbers of naturally-occurring radioactive isotopes are double-underlined; mass numbers of any other
isotopes are single-underlined. Naturally-occurring isotopes are listed in their order of abundance. All other
isotopes are listed in order of decreasing half-life which is discussed later in this chapter.
Element
Mass numbers of isotopes
H 1, 2, 3
He 4, 3, 6, 8
Be 9, 10, 7, 11, 6
B 11, 10, 8
C 12, 13, 14, 11, 10, 15, 16, 9
S 32, 34, 33, 36, 35, 38, 37, 31, 30, 29
N 14, 15, 13, 16, 17, 18
Ca 40, 44, 42, 48, 43, 46, 41, 45, 47, 49, 50, 39, 38, 37
Sn 120, 118, 116, 119, 117, 124, 122, 112, 114, 115, 126, 123, 113,
125, 121, 110, 127, 128, 111, 109, 108, 129, 131, 130, 132
U 238, 235, 236, 234, 233, 232, 230, 237, 231, 240, 229, 239, 228, 227
Lr 260, 256, 255, 254, 257, 256, 252, 251, 258
The simplest element, hydrogen, has three isotopes. The most common form of
hydrogen (protium) has one proton and no neutrons in its nucleus. Its atomic number is 1,
and its mass number is 1. The nuclear notation for protium is shown at right. In nature
approximately 99.985% of all hydrogen atoms are protium.
1 H
1
The remaining 0.015% of hydrogen consists of deuterium atoms. Also known as heavy
hydrogen, deuterium differs from protium in that it has one neutron in the nucleus in addition to one
proton.Using the letter D instead of H as the symbol, write the nuclear notation for deuterium:
{8}_______________ Protium and deuterium are both stable, naturally-occurring isotopes. Water (H2O)
molecules which contain deuterium instead of protium are known as "heavy water" which is sometimes
represented as D2O. About two water molecules in every billion are "heavy." A third form of hydrogen is
man-made and is radioactive. It is known as tritium, and it is a common by-product of the nuclear reactions
that occur in a nuclear power plant. Tritium has two neutrons in its nucleus. Using the letter T instead of H
as the symbol, write the nuclear notation for tritium. {9}________________
28-4 ©1997, A.J. Girondi

1A
Table 28.2
The Radioactive Elements
(All of their isotopes are radioactive)
2A 3A 4A 5A 6A 7A
8A
43
Tc
84
Po
85
At
86
Rn
87
Fr
88
Ra
89
Ac
104
Unq
105
Unp
106
Unh
107
Uns
108
Uno
109
Une
110
Uun
111
Uuu
61
Pm
90
Th
91
Pa
92
U
93
Np
94
Pu
95
Am
96
Cm
97
Bk
98
Cf
99
Es
100
Fm
101
Md
102
No
103
Lr
It is common to identify which particular isotope of an element is being discussed by writing the
mass number after the name of the element with a dash in between. For example, protium is hydrogen-1,
while deuterium is hydrogen-2. Following this method, how would tritium be written?
{10}_______________ What is meant by mass number? {11}___________________________________________________
SECTION 28.2 Four Types of Nuclear Reactions
The equation at right represents a nuclear change. We will refer to
it as a nuclear equation. More specifically, it depicts the change of an atom
of carbon-14 into an atom of nitrogen-14:
14
6
14
C -----> N + e
7
0
-1
Nuclear equations often include a special type of notation to represent subatomic
particles such as electrons, protons, and neutrons. This notation looks similar to
nuclear notation which represents a nucleus, but it is not the same. The
notations describing an electron, a proton, and a neutron are shown below. Note
that the superscripts represent the mass numbers of each particle. The mass
number of an electron is zero. However, the subscripts represent the charge on
the particle. Note that neutrons have no charge, so the subscript for them is zero.
Thus, the difference between nuclear notation and the notation for these
subatomic particles lies in the meaning of the subscript.
electron:
proton:
neutron:
0
-1 e p
1
+1
1
n
0
28-5 ©1997, A.J. Girondi

mass number
atomic number
14
mass number
C p
6 charge +1
1
NUCLEAR NOTATION
SUBATOMIC PARTICLE NOTATION
According to the data in Table 28.1, is carbon-14 a radioactive isotope? {12} _________ How about
nitrogen-14? {13} _________ Note that if the atomic number changes during a nuclear reaction, the
identity of the resulting element changes, too. In the equation shown below, a nucleus of carbon
becomes a nucleus of nitrogen as the atomic number changes from 6 to 7. An electron is also given off as
a product. But hey! If the atomic number changes from 6 to 7, this means that one addition proton is now
present. Where did it come from? Hmmmm.
14
14 0
C -----> N + e
6
7 -1
Electrons are sometimes called beta particles (pronounced "bay-ta"). So, the giving off of an
electron in a nuclear reaction is called a beta emission. In order for carbon-14 to change to nitrogen-14,
there was an increase in the number of {14} _________________ in the nucleus. When a neutron
decomposes, the products are a proton and an electron. The new proton causes the atomic number to
increase by one, and the electron is given off. When the decomposition of a neutron produces a proton,
the mass number remains unchanged. Since one element is changed into another in this reaction, this
particular type of nuclear reaction is called a {15} ____________________________.
There are four types of nuclear reactions that release energy:
1. Natural Radioactive Decay
Natural radioactive decay refers to the ability of a nucleus to decompose (decay) and give off
energy spontaneously (without any external stimulation). As a result, the number of {16} ______________
(atomic number) in the nucleus may increase or decrease, depending on the type of radioactive decay.
The equation below in which carbon-14 is converted to nitrogen-14 represents a natural radioactive
decay.
14
14 0
C -----> N + e
6
7 -1
2. Artificial Transmutation
During artificial transmutation, a nucleus changes its identity as a result of some external
stimulation created by man. For example, an external particle such as a neutron could be used to bombard
the nucleus, causing it to decompose. This kind of nuclear disintegration results in the formation of an
artificial (man-made) isotope of the element. The equation below shows the conversion of natural
nonradioactive cobalt-59 to radioactive cobalt-60 by a process known as slow neutron bombardment.
59
Co +
27
1
n
0
---->
60
Co
27
Notice that since a neutron is being added to the nucleus, the mass number of the nucleus increases by
one, from 59 to 60. The atomic number remains unchanged since the number of {17}______________________ is
unchanged. Since the atomic number remains unchanged, the identity of the nucleus (cobalt) remains
the same. What we have done here is to change one isotope of cobalt into a different isotope of cobalt.
28-6 ©1997, A.J. Girondi

3. Fission
In fission, a nucleus with a large mass splits into two nuclei with smaller masses. To cause fission,
man bombards certain nuclei with special particles. The fission process is used to generate heat in nuclear
power plants, and is the kind of reaction which occurs during the explosion of an atomic bomb. Let's see
where this energy comes from. Look at the equation below which represents the fission of uranium- 235.
Find the total of the mass numbers of the two particles on the left side of the equation: {18} __________.
235
U +
92
1
n
0
138
----> Ba +
56
95
Kr +
36
1
3 n + energy
0
Next, find the total of the mass numbers of the five particles on the right side: {19} __________. How do
these totals compare? {20} ______________________________ As a result, you would think that mass
the amount of matter) is conserved (neither created nor destroyed). However, this is a bit misleading.
Keep in mind that the mass number is the total number of the protons and neutrons in the nucleus, not
their exact total mass. Remember that masses of atoms and subatomic particles are expressed in very tiny
units called atomic mass units (amu). The mass of an atom of U-235 is actually a little greater than 235 amu,
and the masses of Ba-138 and Kr-95 are actually a little less than 138 and 95, respectively. Therefore, in
the equation above, there is a small loss of mass which appears as a great amount of energy. In other
words, some mass is converted into energy. An atomic bomb gives off a tremendous amount of heat
because some mass is converted into energy. A tiny amount of mass can produce a tremendous amount
of energy. When the uranium nucleus splits into smaller nuclei, the energy which was needed to hold the
whole thing together in the first place is no longer needed. This is the energy which is given off.
4. Fusion
When fusion occurs, the nuclei of two lower mass elements are combined to form a nucleus with a
greater mass representing a different element. Exceedingly high temperatures are needed to cause
fusion to occur, since the two nuclei repel each other due to their similar positive charges. Fusion
reactions are the source of the sun's energy where hydrogen nuclei combine to form helium nuclei. The
equation below shows the fusion of 2 deuterium nuclei to form one helium-4 nucleus (also called an alpha
particle).
2 2
4
H + H -------> He + energy
1 1
2
Fusion reactions were used in weapons such as the hydrogen bomb. Scientists are experimenting with
fusion reactions in devices known as breeder reactors which may someday replace fission reactors in
nuclear power plants. Fusion, like fission, results in a loss of mass which is converted into a great amount
of energy. However, fusion releases much more energy per gram of fuel than fission does.
Problem 1. Let's practice writing nuclear notation. Keep in mind that the superscript is the mass
number (sum of protons and neutrons) and the subscript is the atomic number (number of protons) if the
particle is a nucleus. If the particle is a subatomic particle (proton, electron, or neutron,) then the subscript
is the charge on the particle. Write the nuclear notation for each of the following:
a. an isotope of carbon (C) which contains 6 protons and 8 neutrons
b. an isotope of helium (He) which contains 2 protons and 4 neutrons
c. an isotope of uranium (U) which contains 92 protons and has a mass number of 233
d. an isotope of tin (Sn) which contains 50 protons and 60 neutrons
a.____________ b.____________ c.____________ d.____________
28-7 ©1997, A.J. Girondi

Now, let's try working with some nuclear equations. Keep in mind that in a balanced nuclear
equation, the total of the superscripts of all particles must be equal on both sides of the equation. The
sum of the subscripts of all particles must also be equal on both sides. For example, consider the
equation below.
226
222 4
Ra -----> Rn + He
88
86 2
In this example, an isotope of radium (Ra) decomposes into an isotope of radon (Rn), and this
decomposition is accompanied by the emission of a helium nucleus which is also called an alpha particle.
What is the sum of the superscripts on the right side of the equation? {21}_______________ How does this
compare with the superscript on the left side? {22} _____________________ What is the sum of the
subscripts on the right side? {23}__________________ How does this compare to the subscript on the left side?
{24}___________________________________ Is this nuclear equation balanced? {25}_________________
Problem 2. Complete the following transmutation reactions, indicating in each case, the nuclear
notation of the element formed. What element is formed in the first equation below? Well, if you check it
out, the atomic number of the missing particle will have to be 6. What element has an atomic number of 6?
{26}________________________ Therefore, what element symbol will the missing particle have? {27}________________
a.
9
Be
4
4
+ He -----> + n
2
1 0
b.
28
Si
4
2
+ D -----> + n
1
1 0
27
c. Al + n -----> +
13
1 0
4
He
2
55
2
d. Mn + D -----> + 2 n
25
1
1 0
e.
24
Na
11
-----> +
0
-1 e
Complete the following equations indicating in nuclear notation, in each case, what particle - if any - was
ejected. Answers may include:
0
electron: e -1 proton: 1 p neutron:
1 4
n alpha particle: He
+1
0
2
14
f. N + n -----> +
7
1 0
11
B
5
g.
9
Be
4
2
+ D -----> +
1
10
B
5
28-8 ©1997, A.J. Girondi

27
h. Al
13
4
+ He -----> +
2
30
P
15
i.
239
U
92
239
-----> Np +
93
The radioactive elements with atomic numbers 84 through 92 (up to and including uranium) have
some naturally-occurring radioactive isotopes. The elements beyond uranium (with atomic numbers
greater than 92) do not have any naturally occurring isotopes. These elements beyond uranium are
known as the transuranium elements. They are all synthetic elements since all of their isotopes are manmade.
Most of the radioactive elements (with atomic numbers 84 and above) are too unstable to be
assigned an atomic mass (atomic weight). If you look at a periodic table, you will notice that the atomic
masses of these elements are given in parentheses. (Check this out on a periodic table now.) The
number in the parentheses represents the atomic mass of the single most stable isotope. You will recall
that atomic mass is defined as the average mass of the various naturally occurring isotopes of an element
in the proportions in which they occur in nature. The radioactive isotopes of elements with atomic
numbers 84 and above are constantly decomposing. These isotopes have different half-lives, which
means that they are decomposing at different rates. Use this information to explain why these elements
cannot have an atomic mass as defined above:
{28}________________________________________
______________________________________________________________________________
Most elements with atomic numbers smaller than 84 are stable because NONE of their naturallyoccurring
isotopes are radioactive. There are some exceptions to this rule. For example, K-40 and Ca-46
are radioactive. Most of the elements below atomic number 84 are stable enough to be assigned an
atomic mass. (Elements #43 and #61, Technetium and Promethium, are exceptions.) Man-made
radioactive isotopes have been synthesized for many of these elements, but synthetic isotopes are not
included in the calculation of atomic masses since they are not found in nature.
Section 28.3 Early Studies of Radioactivity
In1896, a French scientist by the name of Henri Becquerel accidentally discovered natural
radioactivity while conducting experiments with a uranium compound called potassium uranyl. In one of
his experiments, Becquerel wrapped a photographic plate in black, lightproof paper and placed some of
the uranium compound on top of the covered plate. He then placed this arrangement in the sunlight.
Although the sunlight could not pass through the lightproof paper, the plate became exposed in the area
of the uranium compound, as indicated by a dark area on the photograph. Becquerel thought that
perhaps energy from the sun had been changed into some more penetrating form which was able to pass
through the paper. He then attempted to repeat the experiment, but cloudy weather prevented him from
doing so at that time. He decided to store his second set-up in a closed drawer. Later, on a sunny day,
Becquerel repeated the experiment using a fresh photographic plate instead of the one he had stored in
the closed drawer. He then developed both of the photographic plates. Since the stored plate had not
been exposed to sunlight, Becquerel expected the developed photograph to be blank or almost blank.
Instead, he found that it had a dark area like that of the fresh plate which had been exposed to sunlight.
Becquerel reasoned that the uranium compound must have emitted some type of energy on its own
without the stimulation of sunlight. This ability of a nucleus to emit energy spontaneously (without
external stimulation) is called natural radioactivity. Uranium ore exhibits natural radioactivity with the
greatest amount of energy coming from its most abundant naturally-occurring isotope, U-238.
28-9 ©1997, A.J. Girondi

Becquerel also discovered that as the energy is emitted from a radioactive nucleus and passes
through molecules of oxygen and nitrogen in the air, it causes these molecules to lose electrons, forming
positively charged ions. As a result, the air becomes ionized. The fact that radioactive nuclei can ionize
gases is a principle used in the construction of equipment which can detect the presence of radioactivity.
You probably have a smoke detector in your home. The most common form of smoke detector contains a
small sample of a radioactive element (probably americium). The radiation emitted is capable of ionizing
small particles in the air. When enough particles are present (as during a fire), the ions which are produced
allow an electric current to form and the alarm goes off.
An electroscope is a device which can detect and store an electric charge. See Figure 28.1. A
simple electroscope can be constructed by attaching two pieces of thin metal foil to a metal rod. This
apparatus is then sealed inside a glass container such as a jar. When the electroscope is in its normal
"uncharged" state, the two pieces of metal foil will hang beside each other. To convert the electroscope
to its "charged" state, we have to supply it with an excess of electrons. How do you do this? Well, there
are many ways. Even by combing your hair and then touching the comb to the metal rod on the
electroscope will do it. The electrons on the comb (which came from your hair) will flow into the rod and
into the two pieces of metal foil. At that point, both pieces of foil would carry a negative charge and they
would repel each other. The greater the amount of charge they hold, the more they repel each other. So,
an electroscope is a crude device for detecting and measuring an electrical charge. The air around the foil
in the electroscope acts as an insulator, helping to prevent the electroscope from losing its stored charge
right away. It is much harder for electrons to flow through air than through metal. If you touch the metal rod
on the electroscope with any substance which is a good "acceptor" or conductor of electrons (such as a
piece of metal), the excess electrons will flow out of the electroscope which will then lose its charge.
discharged weakly charged highly charged
Figure 28.1
An Electroscope
When nuclear radiation ionizes the air forming positively-charged particles, these positive particles
can draw negatively-charged electrons away from an electroscope in which they might be stored. It is
possible to measure the rate at which radioactive emissions occur by measuring the rate at which an
electroscope loses its charge. Marie Sklodowska, a student of Becquerel, used an electroscope to study
the radioactivity of uranium and its various ores. She found that one uranium ore, pitchblende, gave off
28-10 ©1997, A.J. Girondi

much more radioactivity than even pure uranium. After her marriage to the physicist Pierre Curie, they
both studied the radioactivity of pitchblende. The Curies discovered that the increased radioactivity of
pitchblende was due to the presence of two elements in the ore. Madame Curie called the first radioactive
element which they discovered in the ore "polonium" after her native land, Poland. Find polonium (Po) on
the periodic table. What is its atomic number? {29}_______________ On the periodic table, the mass number of
polonium is (210). What is so special about Po-210 and why is this mass number given in parentheses?
It took the Curies four years to complete the processing of the ore from which they extracted only 0.1 gram
of the second radioactive element, radium, in the form of radium chloride. Radium (Ra) has what atomic
number on the periodic table? {30} ___________ Its mass number is given as (226). Both polonium and
radium were found to be more radioactive than uranium. Although the use of the electroscope allowed
the Curies to measure the rates at which radiation was emitted, it did not provide any indication as to the
nature of the radiation. In other words, it did not indicate whether the radiation consisted of energy, or
particles, or both.
In 1903, Ernest Rutherford performed an experiment which provided some new information
about the properties of radiation. He placed a piece of pitchblende into a hole drilled deep into a block of
lead. (See Figure 28.2) Most of the radiation emitted by the pitchblende was absorbed by the lead. Only
the radiation that was traveling in a straight line through the hole could escape. A photographic plate was
positioned in the path of the escaping radiation. When the plate was developed, a small single spot
appeared where it was struck by the radiation.
Next, Rutherford placed the poles of a U-shaped magnet at right angles to the stream of radiation.
This forced the radiation to pass through a magnetic field. Since a magnetic field deflects oppositely
charged particles in opposite directions, it was possible to determine the charge of any particles in the
radiation. Streams of radiation which do not contain particles would not be affected by the magnetic field.
When the magnetic field was used, three distinct spots were produced. (See figure 26.2.) The three
spots indicated that the magnet had separated the radiation into three distinct streams. Two streams were
deflected in opposite directions, whereas one stream was not deflected at all. How many of these three
streams contained particles? {31} __________ Why were the two affected streams deflected in opposite
directions? {32} ___________________________________________________________________
The two deflected streams are called alpha (∝) and beta (ß) radiation in Figure 28.2. The unaffected
stream was called gamma (∂) radiation. What must be true about the stream of gamma radiation that was
not deflected? {33}_________________________________________________________________________________________________
photographic plate
photographic plate
radiation
single
spot
formed
(–) (+)
3 spots
formed
magnet
pitchblende
radiation
pitchblende
Lead
Lead
Figure 28.2
Rutherford's Study of Radiation from Pitchblende
28-11 ©1997, A.J. Girondi

The particles which were deflected only slightly in a
direction indicating a positive charge were called alpha particles.
The Greek symbol for alpha is: ∝. The fact that they were only
slightly deflected indicated that they had a relatively large mass
compared to beta particles. In later experiments, it was shown
that alpha particles were actually bundles composed two protons
and two neutrons. They have the same structure as helium
nuclei. You can say that the term alpha particle is another name
for a helium nucleus. Alpha particles are, therefore, designated
by the same nuclear notation as is the most common isotope of
helium which is helium-4. Alpha particles travel at 10,000 to
20,000 miles per second, but can be stopped by a sheet of
paper. They have a great ability to cause ionization by knocking
electrons loose from atoms or molecules through which they
pass.
4
He
2
Nuclear Notation for Helium-4
or for an Alpha Particle
The very low mass particles were deflected much more than the alpha particles and in the
opposite direction. Apparently, they were negatively charged. Rutherford called them beta particles. The
Greek symbol for beta is: ß . They were later shown to be electrons which travel at a rate of up to 100,000
miles per second! Their ability to penetrate matter when they strike it is much greater than that of alpha
particles; nevertheless, they still cannot penetrate more than a few inches of solid material. Beta particles
cause much less ionization than alpha particles.
The radiation emitted between the alpha and beta streams was not deflected at all by the magnetic
field and, therefore, carries no electric charge. This stream was called gamma radiation. The Greek symbol
for gamma is: ∂. Gamma rays are similar to x-rays, but are higher in energy. Their penetrating power is
much greater than either alpha or beta radiation, and they can penetrate almost one foot of solid lead!
Gamma rays travel at the speed of light (186,000 miles per second). They cause practically no ionization at
all when they interact with atoms or molecules. Table 28.3 summarizes some of the information
presented about the three forms of radioactivity. Complete the column headed "Penetrating Power" by
inserting the terms high, low, and moderate in the proper slots. Next, complete the column headed
"Ionizing Power" by inserting the terms high, moderate, and almost none in the proper slots.
Table 28.3
The Three Forms of Natural Radioactivity
Penetrating Ionizing
Decay Product Symbol Charge Power Power
alpha particle
4
He +2
2
{34}_________ {37}_________
beta particle
0
–1
-1
{35}_________ {38}_________
gamma rays none none {36}_________ {39}_________
In general, a radioactive isotope of an element emits alpha particles or beta particles, but not both. The
emission of gamma rays generally accompanies both alpha emissions and beta emissions. Which of the
three kinds of radioactive emissions is needed in order for a transmutation to occur? {40} ______________
Explain: {41} _____________________________________________________________________
______________________________________________________________________________
28-12 ©1997, A.J. Girondi

Name three radioactive elements found in pitchblende: {42} ___________________________________
SECTION 28.4
Methods of Detecting Radiation
Electroscopes
Radioactivity has an effect on matter as it passes through it. We can, therefore, study radioactivity
by recording and measuring these effects. You already know that nuclear emissions can expose
photographic plates and can ionize gases. Some measuring devices make use of the fact that gases will
conduct electricity when they become ionized as a result of exposure to radiation. For example, the
electrical charge stored in an electroscope can be lost when the air inside and around the electroscope
becomes ionized. See Figure 28.3 below.
molecules
of air
ions of air
inside here
incoming radiation
ionizes the air
charged
foil strips
charge
lost
Figure 28.3
Effect of Radiation on Stored
Charge
Ionization chambers
In an ionization chamber, radiation passes through a gas. The radiation causes the gas particles to
be split into pairs of ions which are then collected on the surfaces of oppositely charged electrodes. The
number of pairs of ions produced can be measured. An example of a measuring instrument using this
principle is the self-reading dosimeter. With such a device, radiation can be measured in units called
Roentgens. This may sound a bit complicated, but a Roentgen is the amount of gamma radiation required
to produce 1.61 X 10 12 pairs of ions when it is absorbed by 1 gram of air.
Geiger Counter
A Geiger counter (more accurately known as a Geiger–Mueller counter) consists of a sealed tube
containing argon gas at a low pressure. One end of the tube contains a thin glass window. There are two
electrodes in the tube (see Figure 28.4). The negative electrode is a metal cylinder located just inside the
tube. The positive electrode is a wire which runs down the center of the cylindrical tube. A high voltage
exists between these electrodes, but electric current does not flow, since the uncharged (un-ionized)
argon gas atoms cannot carry the current from one electrode to the other. When radiation enters through
the thin window, it ionizes some of the argon atoms, forming argon ions and free electrons. The argon
ions become conductors of electric current between the electrodes. The electrical impulses are then sent
into an amplifier. From there they may be sent to a counter or to an amplifier to be converted into sounds
or flashes of light.
28-13 ©1997, A.J. Girondi

negative
electrode
positive
electrode
argon gas
incoming
radiation
thin glass
window
1000 Volts
Figure 28.4
Geiger Counter
To
amplifier or
counter
Photographing Particle Trails
As you know, fast moving charged particles such
as those present in radioactive emissions can cause the
formation of ions when they collide with molecules through
which they pass. If this process occurs in a container which
is saturated with water vapor, the water molecules can
condense on ions forming tiny spots of fog. This fog forms
along the paths of the radioactive emissions since that is
where the ions form. These foggy paths are visible to the
eye. They are called trails. Photographs of these particle
trails enable scientists to study how certain decays occur.
The device in which all this takes place is called a cloud
chamber. In Figure 28.5, the curved vertical line
represents the path of a subatomic particle passing
through a thin sheet of lead. The path is curved due to the
presence of a strong magnetic field in the cloud chamber.
Figure 28.5
Particle Trails in a Cloud Chamber
Scintillation Counter
When radiation strikes fluorescent substances (known as phosphors) it causes flashes of light to
be emitted. This is what happens in a fluorescent light bulb or on a television screen. There are
instruments which can count these small flashes of light, and in this way, measure radiation. The process
of producing light flashes is called scintillation. The devices are called scintillation counters.
28-14 ©1997, A.J. Girondi

Section 28.5 More Practice With Nuclear Equations
Problem 3. Complete the equations below, and make sure that they are balanced.
14
N
7
a. + He
4
2
-----> 17 8 O +
9
b. Be + He
4 2
4
-----> 12 6 C +
c. 3 H
1
-----> 3 2 He +
23
Na
11
d. + He
3
2
----->
1
1 H +
e. + He
3
2
----->
1
0 n +
13
N
7
Now, complete the equation below. Does anything appear strange? An electron with a positive charge!
30
f. P
15
-----> 0
+1 e +
Yes, there is such a thing as an electron with a positive charge. It's call a positron. As you can imagine,
there's a lot more to know about nuclear chemistry!
SECTION 28.6
Learning Outcomes
This is the end of Chapter 28. The subject of nuclear chemistry is continued in Chapter 26.
Review the learning outcomes below. When you feel that you have mastered them, arrange to take the
exam on Chapter 26, and then move on to Chapter 27.
_____1. Define and /or describe nuclear terms including: isotope, transmutation, alpha particle, beta
particle, gamma rays, fission, fusion, radioactivity, Geiger counter, scintillation counter, and cloud
chamber.
_____2. Write the nuclear notation of nuclear particles and of the nuclei of atoms given mass numbers,
atomic numbers, or other relevant data.
_____3. Describe the historical contributions of Becquerel, Madame and Pierre Curie, and Rutherford.
_____4. Given sufficient information, complete and balance nuclear equations.
_____5. Be able to locate the radioactive elements on the periodic table.
28-15 ©1997, A.J. Girondi