Topic 1 - Matter and Energy - Revsworld

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Topic 3 - The Atomic Structure
17. Isotope symbols: Determining and comparing particles in isotope symbols
In any given isotope notation, you should be able to determine the following information.
. Mass number, number of nucleons, and the sum of protons and neutrons
. Atomic number, number of protons, nuclear charge, and number of electrons
. Number of neutrons
When two isotope symbols are given, you can determine and compare the number of particles between
them.
Below, an isotope of sulfur and an isotope of phosphorous are given.
As you study the information below:
Note the differences and similarities in the number of particles between the two isotopes.
Number of Protons + neutron
Number of Nucleons
34 Mass number 33
S
16 Atomic number 15
Number of protons
Nuclear charge
Number of electrons (if neutral)
_________________________________________
18 Neutrons (top # - bottom #) 18
P
According to information from the isotope
symbols, the following comparisons can be
made:
34 S has more nucleons than 33 P
33 P has one fewer proton than 34 16 15 S
34 S has a greater nuclear charge than 33 P
P-33 has the same number of neutrons
as S-34
as
18.Isotope symbols: Determining and comparison number of particles in isotope symbols
Concept Tasks: Be able to determine the number of subatomic particles from a given isotope notation.
Be able to compare the number of subatomic particles of two given isotope symbols.
Example 10
To correctly determine and compare number of particles in isotope symbols, you
must know where to look isotope symbols. (see above notes)
The use of your Periodic Table is also recommended.
What is the total number of protons and neutrons
in the nuclide 80 Br
1) 35 2) 80 3) 45 4) 115
Answer: Choice 2. Top number (80) is the mass number.
Mass number = Protons + neutrons
Example 11
35
The nucleus of the atom
1 07
Ag contains
1) 60 neutrons and has a nuclear charge of +47
2) 60 electrons and has a nuclear charge of +47
3) 47 neutrons and has a nuclear charge of +107
4) 47 electrons and has a nuclear charge of +107
Example 12
Which nuclide contains the greatest number of
neutrons?
1) 207 Pb 2) 84 Kr 3) 207 Ti 4) 208 Bi
Before choosing:
Determine atomic number (bottom #) for each.
Subtract bottom from top to get # of neutrons
207 Pb
84 Kr
207 Ti
208 82 36 81 83Bi
Neutrons = 125 48 126 125
Answer: Choice 3.
Example 13
Which nuclide contains 20 protons?
1) Ca-40 3) B -10
2) Ne-20 4) He-5
Answer: Choice 1. Ca has an atomic
number of 20
20 protons = atomic number 20
Answer: Choice 1. Ag has atomic number of 47.
+47 Nuclear charge = atomic number 47
60 neutrons = 107 – 47
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