Atoms that differ in the number of neutrons are referred to as what?

Atoms that differ in the number of neutrons are referred to as isotopes. Isotopes are variations of a particular chemical element that have the same number of protons but a different number of neutrons, resulting in different atomic masses. For example, carbon-12 and carbon-14 are both isotopes of carbon; they each have 6 protons, but carbon-12 has 6 neutrons while carbon-14 has 8 neutrons.

In contrast, molecules refer to two or more atoms that are chemically bonded, ions are atoms or molecules that have gained or lost electrons and thus possess a charge, and elements are substances that consist of only one type of atom. While isotopes are variations of elements, the other terms describe different concepts in chemistry that do not specifically relate to the number of neutrons in an atom.