Question

Element X has two naturally occurring isotopes. The isotope with mass 62.93 amu has a
relative abundance of 69.2%. The isotope with mass 64.93 amu has a relative
abundance of 30.8%. Calculate the average atomic mass of Element X. What is the
identity of Element X?

Answer 1

Answer: the average atomic mass is 63.546. The element is copper.

Explanation:
To solve this, you multiply the mass of each isotope by its relative abundance as a decimal (for this question, it would be 62.93 * .692 and 64.93 * .308), then you add the two results together. That gives you the average atomic mass. Then, you look at the periodic table to find which element the mass matches to. If there is none, check your math.