Final answer:
Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons.
Step-by-step explanation:
An element that has an irregular amount of neutrons is called an isotope. Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. For example, carbon-12 and carbon-14 are isotopes of carbon, with carbon-14 having two extra neutrons in its nucleus.