Question

isotopes of the same element are different from one another in that
multiple choice
only one of the isotopes is matter.
they have a different number of protons.
they are a different element.
they have a different number of electrons.
they have a different number of neutrons.

Explanation:

Isotopes of an element have the same number of protons (defining the element), but different numbers of neutrons. All isotopes are matter. Changing the number of protons makes a different element, and typically isotopes have the same number of electrons in a neutral state.

Answer:

They have a different number of neutrons.