Isotope

[Sarah]

Each [element] has many versions that contain a different number of neutrons in the nucleas. Each different version of [the element] is called an [isotope].

[Ernesto]

Each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei, and hence differ in relative atomic mass but not in chemical properties; in particular, a radioactive form of an element.

[Raeanne Dimick]

a form of an atom that has a different atomic weight from other forms of the same atom but the same chemical structure: