chemical element

https://doi.org/10.1351/goldbook.C01022
  1. A species of atoms; all atoms with the same number of protons in the atomic @N04256@.
  2. A pure @C01039@ composed of atoms with the same number of protons in the atomic @N04256@. Sometimes this concept is called the elementary substance as distinct from the chemical element as defined under 1, but mostly the term chemical element is used for both concepts.
Source:
Red Book,3rd ed., p. 35 [Terms] [Book]