Average Atomic Mass Worksheet

Name______

For each of the following, find the average atomic mass using the mass of the individual isotopes and the percent abundance. Note: some of these are real elements & numbers. Others are imaginary. Don’t try to use the periodic table to cheat.

1.

Isotope / Mass / % Abundance
Mg – 24 / 24 amu / 78.70%
Mg – 25 / 25 amu / 10.13%
Mg – 26 / 26 amu / 11.17%

2.

Isotope / Mass / % Abundance
B – 10 / 10 amu / 19.91%
B – 11 / 11 amu / 80.09%

3.

Isotope / Mass / % Abundance
Cu – 63 / 63 amu / 69.2%
Cu – 65 / 65 amu / 30.8%

4.

Isotope / Mass / % Abundance
Pg – 25 / 25 amu / 9.2%
Pg – 26 / 26 amu / 13%
Pg – 28 / 28 amu / 77.8%

5.

Isotope / Mass / % Abundance
Cl – 35 / 35 amu / 73.5%
Cl – 37 / 37 amu / 26.5%

6.

Isotope / Mass / % Abundance
U – 234 / 234 amu / 0.0058%
U – 235 / 235 amu / 0.71%
U – 238 / 238 amu / 99.23%