Question

The relative atomic masses of the elements are usually not whole numbers because:

• A. the methods for determining relative atomic masses are not very accurate
• B. it is often impossible to obtain a pure sample of an element
• C. most elements occur naturally as a mixture of isotopes
• D. the number of neutrons present in the nucleus of an atom often differs from the number of protons present in it

Answer 1

The correct option is C most elements occur naturally as a mixture of isotopes

The relative atomic mass of an element is an average value for the isotopes of the element. For example, the a.m.u for chlorine is $35.5$ because it contains two different isotopes.

Chlorine has two isotopes:$C{l}^{35}$ and $C{l}^{37}$. They exist in the ratio $3:1$. So the average molecular weight comes out to be $35.5$.