Isotope

How to spell isotope

7 letters · 3 syllables

How to pronounce isotope

Say the part in capitals loudest.

What does isotope mean?

1. nounOne of two or more forms of a chemical element that share the same number of protons but differ in the number of neutrons.

Isotope in a sentence

• The hospital uses a radioactive isotope to image the patient's thyroid.

• Carbon dating relies on measuring a particular isotope of carbon in old material.

Where does isotope come from?

Language of origin: Greek

This word comes from the Greek roots isos, meaning 'equal' or 'the same', and topos, meaning 'place'. It was coined in 1913 by the chemist Frederick Soddy, who needed a name for atoms of the same element that have the same chemical behaviour but different atomic weights. The actual word was suggested to him by Margaret Todd, a Scottish physician, who reasoned that these atoms occupy the very same place in the periodic table; 'equal place' captured that idea neatly. The same iso- element shows up in everyday science vocabulary such as 'isobar' and 'isometric', while topos survives in 'topic' and 'topography'. Remembering that the word means 'same place' helps fix the iso- opening and the single -tope ending in the mind.

How the word is built

• iso- (from Greek isos: equal)
• -tope (from Greek topos: place)