Question

Why is the atomic mass of chlorine quoted on the Periodic Table NON-INTEGRAL?

Answer 1

All chlorine nuclei have 17 protons in their nucleus. Chlorine nuclei contain differing numbers of neutrons. The weighted average of the nuclei sum to `35.45` amu.

Explanation:

Isotopic breakdown of chlorine: `""^35Cl`, 75.77%; `""^37Cl`, 24.27%. These are the major isotopes and their weighted average is the quoted atomic mass.