Average Atomic Mass Warm-up

The two naturally occuring isotopes of Europium are ¹⁵¹Eu with a mass of 150.92 amu and an abundance of 47.81%
and ¹⁵³Eu with a mass of 152.92 amu and an abundance of 52.19%. Calculate the Average Atomic Mass.

Solution:
150.92 amu x 0.4781 = 72.15 amu (4 sf)
152.92 amu x 0.5219 = 79.81 amu (4 sf)

Sum the contributions from each isotope:
72.15 amu + 79.81 amu = 151.96 amu (2 decimal places)

Note that this value matches the periodic table.