Question

Which property of an element is always a whole number 

(a) Atomic weight

(b) Equivalent weight 

(c) Atomic number

(d) Atomic volume

Answer 1

Correct option is (c) Atomic number

Atomic weight is the mass of a single atom of an element. It may be fractional. Atomic radius (distance from an atom's nucleus to the outermost orbital of electrons) and atomic volume (average volume of one atom of an element) can be fractional as well. 

Atomic number is the number of protons or electrons in an atom. Since this is countable, it's always a whole number. So, atomic number is the correct answer.