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Procedure: In this investigation, you will determine the percentage of the isotopes of “pennium” and the masses of each isotope in the sample of “pennium” which is given to you. You will then use this information to calculate the average atomic weight of “pennium”.

Pre-lab Questions:

1. The bag of 20 pennies represents a sample of “pennium”.
2. The difference in the masses represents isotopes.
3. You would need to know the number of protons and neutrons.

Data Table

Penny Year Mass (g)
1 1976 3.21
2 1977 3.21
3 1980 3.2
4 1981 3.29
5 1986 2.65
6 1989 2.66
7 1990 2.65
8 1990 2.75
9 1991 2.64
10 1992 2.63
11 1992 2.69
12 1994 2.7
13 1995 2.69
14 1995 2.7
15 1998 2.69
16 1999 2.69
17 1999 2.69
18 2001 2.69
19 2001 2.7
20 2001 2.71

Analysis Questions:

1. The number of isotopes of “pennium” that are present is two isotopes.
2. The evidence for the isotopes in present in the years they were minted. The years 1976 to 1981 showed masses of an average of 3.22g; this represents isotope 1. The years 1986 to 2001 showed an average mass of 2.68g and represents isotope 2.
3. Isotope 1 made up 20% of the sample while isotope 2 made up 80% of the sample.
4. Isotope 1 had an average mass of 3.22g. Isotope 2 had an average mass of 2.68g
5. The average weight of “pennium is 2.79g.