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{{short description|Any type of particle that can undergo a chemical process}}In chemistry and physics, a molecular entity, or chemical entity, is “any constitutionally or isotopically distinct atom, molecule, ion, ion pair, radical, radical ion, complex, conformer, etc., identifiable as a separately distinguishable entity”.{{GoldBookRef|title=molecular entity|file=M03986}} Chemical species is the macroscopic equivalent of molecular entity and refers to sets or ensembles of molecular entities.According to IUPAC, “The degree of precision necessary to describe a molecular entity depends on the context. For example ‘hydrogen molecule’ is an adequate definition of a certain molecular entity for some purposes, whereas for others it is necessary to distinguish the electronic state and/or vibrational state and/or nuclear spin, etc. of the hydrogen molecule.”

See also

• New chemical entity
• Chemical Entities of Biological Interest

Notes and references

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