isotope

Meanings

1. 1
   noun

   one of two or more atoms with the same atomic number but with different numbers of neutrons

2. 2
   noun

   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.

3. 3
   verb

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

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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