isotope

Etymology 1

From iso- (“equal”) + -tope (“place”), because the different isotopes of a chemical element always occupy the same position in the periodic table of elements. The term was coined by Scottish doctor Margaret Todd in 1909 and first used publicly on February 27, 1913 by English chemist Frederick Soddy.

noun

1. (nuclear physics) Any of two or more forms of an element where the atoms have the same number of protons, but a different number of neutrons within their nuclei. Thus, isotopes have the same atomic number but a different mass number.

Etymology 2

Possible back-formation from isotopy.

verb

1. (topology, transitive) To define or demonstrate an isotopy of (one map with another).