Element A exists in three isotopic forms with masses of 21.0, 25.0 and 26.0 amu, respectively. Element Q also exists in three isotopic forms with masses of 20, 24.0 and 25.0 amu, respectively. It is true that:
A) Element A has a lower atomic mass than element Q since it has the lightest isotope.
B) Elements A and Q have identical atomic masses since the sums of their isotopic masses are equal.
C) Element Q has a higher atomic mass than element A since its atomic masses are closer together.
D) More than one correct response.
E) No correct response.

Question

Quizplus · Accepted Answer

The average atomic mass of an element depends on both the masses and the relative abundances of its isotopes, not just the sum of the isotopic masses or the mass of the lightest isotope. Since information about the relative abundances of the isotopes is not provided, none of the statements can be determined to be true.

Element a Exists in Three Isotopic Forms with Masses of 21.0