tap / space
Classic usage
Estimated CEFR level: C2 — Proficiency
Estimated from word frequency; not an official CEFR classification.
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.
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tap / space
Classic usage
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