What are isotopes?

Isotopes are defined as versions of the same element that have the same number of protons but differ in the number of neutrons within their nuclei. This difference in neutron count results in variations in the atomic mass of the isotopes while maintaining the same chemical properties since the chemical behavior of an element is primarily dictated by its electron configuration, which is determined by the number of protons.

For example, carbon has several isotopes, including Carbon-12, which has 6 neutrons, and Carbon-14, which has 8 neutrons. Both isotopes are carbon, as they each have 6 protons, but their differing neutron numbers lead to different atomic masses and slightly different nuclear properties.

The other options suggest different concepts that do not correctly define isotopes. Elements with the same number of neutrons are not defined as isotopes; they would instead be considered a particular isotopic family of different elements. The idea of different elements being chemically bonded refers to compounds rather than isotopes. Additionally, atoms with equal numbers of protons and neutrons describe a specific scenario but do not capture the essence of isotopes themselves, which are concerned particularly with the variation in neutrons while maintaining the same proton count.