Definition of atomic number noun from the Oxford Advanced Learner's Dictionary


atomic number

BrE BrE//əˌtɒmɪk ˈnʌmbə(r)//
; NAmE NAmE//əˌtɑːmɪk ˈnʌmbər//
(chemistry) Molecules and matter
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the number of protons in the nucleus (= centre) of an atom, which is characteristic of a chemical element. Elements are placed in the periodic table according to their atomic numbers. See related entries: Molecules and matter
See the Oxford Advanced American Dictionary entry: atomic number