atom

https://doi.org/10.1351/goldbook.A00493
Smallest particle still characterizing a chemical element. It consists of a nucleus of a positive charge (Z is the proton number and e the elementary charge) carrying almost all its mass (more than 99.9%) and Z electrons determining its size.
Source:
Red Book, 3rd ed., p. 35 [Terms] [Book]
Citation: 'atom' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.A00493 RIS BibTex EndNote
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