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Added 9 October 2026

isotope

/ˈaɪ.sə.təʊp/ noun

In Latin: none, coined in 1909 Coined: 1909, by Margaret Todd Wiktionary

noun Definition from Wiktionary (CC BY-SA). Pronunciation from Wiktionary, via Kaikki.org. More about isotope at Wordnik → Where our words come from →

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.

verb

To define or demonstrate an isotopy of (one map with another).

Origin

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

From Wiktionary, via Kaikki.org (CC BY-SA)

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