adjective Chemistry.

having one atom in the molecule.
containing one replaceable atom or group.
having a valence of one.

Origin of monatomic

First recorded in 1840–50; mon- + atomic
Related formsmon·a·tom·i·cal·ly, adverb Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

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Historical Examples of monatomic

British Dictionary definitions for monatomic


monoatomic (ˌmɒnəʊəˈtɒmɪk)

adjective chem

(of an element) having or consisting of single atomsargon is a monatomic gas
(of a compound or molecule) having only one atom or group that can be replaced in a chemical reaction
a less common word for monovalent
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

monatomic in Medicine




Occurring as single atoms.
Having one replaceable atom or radical.
Related formsmon′a•tomic•al•ly adv.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.