Question

Are relative atomic masses of elements whole numbers?

Answer 1

An elements exists in its various isotopic forms.

The atomic mass reported on a periodic table is the weighted average of all the naturally occuring isotopes. Being an average it would be most unlikely to be a whole number.

For example, hydrogen comes with a single proton, a proton + a neutron, and a proton + two neutrons. The isotopes with the neutrons occur in very small amounts so the average weight is slightly greater than 1. If the atomic mass is not a whole number, then that means it is an average atomic mass of all the isotopes of the elment's atomic masses.