What term describes atoms that have the same atomic number but different atomic masses?

The term that describes atoms with the same atomic number but different atomic masses is isotopes. Atoms are defined by their atomic number, which corresponds to the number of protons in the nucleus. However, atoms of the same element can differ in the number of neutrons they contain, which affects their atomic mass. These variations lead to the formation of isotopes.

For example, carbon typically has an atomic number of 6, which means it has 6 protons. However, it can exist in forms such as carbon-12, which has 6 neutrons, and carbon-14, which has 8 neutrons. Both of these are isotopes of carbon, characterized by having the same number of protons but different neutron counts and, consequently, different masses.

Other terms, such as isomers, refer to molecules with the same molecular formula but different structural arrangements, which is not the case here. Molecules are formed when two or more atoms bond together, and elements are pure substances consisting of only one type of atom. These definitions do not accurately apply to the scenario of atoms differing in atomic mass while maintaining the same atomic number.