Question

Atomic mass of an element is not a whole number because:

• A. it contains electrons, protons and neutrons
• B. it contains isotopes
• C. it contains allotropes
• D. all of the above

Answer 1

The correct option is B it contains isotopes

Atomic mass of an element is not a whole number because It contains isotopes.
For example, chlorine has two isotopes ${}_{17}^{35}Cl$ and ${}_{17}^{37}Cl$ with natural abundances in the approximate ratio of 3:1. Hence, the average atomic mass of chlorine is approximately 35.5 g/mol.