Question

How can two atoms of the same chemical element be different?

A.
They may be different allotropes of the element. Each allotrope of the same element has a different number of electrons.

B.
They may be different isotopes of the element. Each isotope of the same element has a different number of electrons.

C.
They may be different allotropes of the element. Each allotrope of the same element has a different number of neutrons.

D.
They may be different isotopes of the element. Each isotope of the same element has a different number of neutrons.