ammonium

n. univalent chemical ion (Chemistry)

Ammonium is also an old name for the Siwa Oasis in western Egypt. The ammonium cation is a positively charged polyatomic cation of the chemical formula NH4+. It has a molecular mass of 18.04 and is formed by protonation of ammonia (NH3). The resulting ion has a pK_a of 9.25. Ammonium and aminium are also general names for positively charged or protonated substituted amines and quaternary ammonium cations N+R4, where one or more hydrogen atoms are replaced by organic radical groups (which could be symbolized as R).
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Noun
1. the ion NH4 derived from ammonia; behaves in many respects like an alkali metal ion
(synonym) ammonium ion
(hypernym) ammonia
(derivation) ammonify

n. ammonium, chemical element

n. ammonium (Chemistry), univalent chemical ion