Penny Isotopes

Name
Period
Penny Isotopes
Using the definition of an isotope describe what would have to be different about a penny
to allow it to demonstrate this concept:
Now get ten pennies and fill in the data table below:
Penny observations and Data
Value Year minted Mass Description
Write down three ways you could divide the pennies into two or three groups – explain
your grouping
1.
2.
3.

Name
Period
How did other tables group their pennies differently?
What grouping best fits the definition of an isotope?
Now using that information, find 5 pennies from each group and calculate the average
mass for each
Data Table for Average Mass of Pennies
Penny trial number Mass of old penny Mass of new penny
Average mass of penny
Now calculate the predicted mass of 3 old pennies and 7 new pennies. (show your work)
What would be the average mass of the new group of pennies?
Now find out what value a random sample of pennies most closely matches.
Random mass sample of 25 pennies
Trail
number
Total mass of
25 pennies
Average mass
of 25 pennies
Average that best matches
(Old 1 cent) (New 1 cent) (Random average)

Name
Period
What a scientists says to explain this.
Isotopes are atoms of the same element that have the same properties but have different
masses based on the number of neutrons present. The number of neutrons is generally
equal to or more than the number of protons – with the main exception of Hydrogen, which
usually has one proton and no neutrons.
In Atoms each proton and each neutron has a mass unit of one
A Pure sample of copper (Cu) would consist of
69 % Cu-63
31 % Cu –65
or in 100 atoms there would be ___________Cu- 63 and _____________Cu-65
Since copper has an atomic number of 29, that means it has _________ protons in its
nucleus. Cu – 63 has a mass number of 63, with 29 of that mass due to proton mass. Then
the number of neutrons would have to be _________ to equal the total mass of the isotope
29 + ______ = 63 (mass units)
Copper 65 would still have only _________ protons, because the number of protons in an
element does not change! Instead it would have more neutrons
29 + ______________ = 65; making it heavier by 2 mass units.
To find the Atomic mass of Copper we would need to do some math
(% of isotope Cu-63 in decimal form) times (mass of isotope Cu -63) PLUS
(% of isotope Cu-65 in decimal form) times (mass of isotope Cu -65)
Now Calculate the atomic mass of copper using this information and compare your answer
to the atomic mass of copper in the textbook (periodic table)
Write this formula using the number values and put them on a Sheet of paper to share with
the rest of the class.
Questions:
1. How close does your calculated value for copper match the atomic mass in the
periodic table?
2. What happens to an atom of any element as you add neutrons to its nucleus?
3. Oxygen has an atomic number of 8 and an atomic mass of 15.99.
a. What can you say about most of the oxygen isotopes?

Name
Period
b. About some of the oxygen isotopes?
What Happens to the stability of atoms when the mass increases?
Write a prediction of what will happen when you create one stack of pennies – face down
with 3 pennies (protons) and face up with 3 pennies (neutrons). Then added pennies to
increase the number of protons and neutrons in the stack until you had an atom with 20
protons and 25 neutrons?
MY PREDICTION
Now using the cards given to you write down the information and the results below:
Isotope
A
Isotope
B
Isotope
C
Atomic
Number
Mass
number
Number of neutrons
Results / stability of the stack
What element did you model?
Class Data
Write a conclusion for this question based on the class data (question, answer, data, why
you think this happen)