Question

Which statement concerning elements is true?(1) Different elements must have different numbers of isotopes.

(2) Different elements must have different numbers of neutrons.
(3) All atoms of a given element must have the same mass number.
(4) All atoms of a given element must have the same atomic number.

Answer 1

The correct statement is (4) All atoms of a given element must have the same atomic number.

Atoms come in different isotopes(which have different mass), which differ in the number of neutrons, but are still the same element (this tells you why the other options are bad).