noun

isotope

/ˈaɪ.səˌtoʊp/ · say it: AY·suh·tope

a form of an element with a different number of neutrons

In more detail

1. (noun) one of two or more forms of a chemical element that have the same number of protons but different numbers of neutrons, giving them different atomic weights and sometimes different chemical properties

2. (noun) a radioactive form of an element, often used in medicine or scientific research

Examples

1. Carbon-12 and carbon-14 are isotopes of the same element.
2. Doctors use radioactive isotopes to treat certain cancers.

How to use isotope

Isotope is a technical term used primarily in chemistry, physics, and biochemistry to refer to atoms of the same element with different numbers of neutrons. While the term can denote either stable or radioactive forms, in everyday scientific and medical contexts it often implies a radioactive variant, especially when discussing medical applications or tracers. The word is precise and unambiguous within scientific discourse.

Common phrases

radioactive isotope
stable isotope
carbon isotope
oxygen isotope
isotope analysis
isotope labeling

Synonyms

variant · form · allomorph

Word family

isotopic (adjective) · isotopically (adverb)

A common mistake

Learners sometimes confuse isotopes with isomers; isotopes differ in neutrons (and thus atomic mass), while isomers are molecules with the same molecular formula but different structural arrangements.

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