Which statement is true regarding isotopes?

Isotopes are defined as variants of a particular chemical element that share the same number of protons but differ in the number of neutrons within their atomic nuclei. This distinction leads to different mass numbers for the isotopes, as the mass number is the sum of the protons and neutrons. Since all isotopes of a given element maintain the same number of protons, they represent different forms of that element, highlighting their nuclear variations rather than any change in elemental identity.

The presence of distinct mass numbers among isotopes is crucial in numerous scientific applications, such as dating techniques in geology and archaeology or tracing metabolic pathways in biological research. As a result, knowing that isotopes have the same number of protons but different mass numbers allows one to better understand the behavior and characteristics of different element variants.