Final answer:
The average atomic mass of an element is calculated using a weighted average of the atomic masses and relative abundances of its isotopes. For chlorine, this involves multiplying the mass of each isotope by its abundance and summing these values.
Step-by-step explanation:
To calculate the average atomic mass of an element, you need to know the relative abundances of the isotopes and their individual atomic masses. This calculation involves using a weighted average, where the atomic mass of each isotope is multiplied by its relative abundance in decimal form, and then these products are summed up to provide the average atomic mass of the element.
For example, let's calculate the average atomic mass of chlorine. If we have two naturally occurring isotopes of chlorine: chlorine-35 with an atomic mass of about 34.969 u and a relative abundance of 75.77%, and chlorine-37 with an atomic mass of about 36.966 u and a relative abundance of 24.23%, the calculation would be as follows:
(0.7577 * 34.969 u) + (0.2423 * 36.966 u)
After doing the math, we add these results to find the average atomic mass of chlorine.