If the relative molecular mass of an element is not a whole number, it can be deduced that the element is

If the relative molecular mass of an element is not a whole number, it can be deduced that the element is an isotopic mixture. Isotopes are atoms of the same element that have different numbers of neutrons, which can result in a different relative atomic mass. When an element has isotopes with different masses, the relative molecular mass will not be a whole number. For example, carbon has two stable isotopes, carbon-12 and carbon-13, which means that naturally occurring carbon is an isotopic mixture and has a relative molecular mass that is not a whole number (12.01). Therefore, option D is the correct answer.