• synonyms


adjective Chemistry.
  1. having one atom in the molecule.
  2. containing one replaceable atom or group.
  3. having a valence of one.
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Origin of monatomic

First recorded in 1840–50; mon- + atomic
Related formsmon·a·tom·i·cal·ly, adverb
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for monatomic

Historical Examples

  • If this should prove to be the case, it will favour the view that chlorine itself is molecular and not monatomic.

    Fragments of science, V. 1-2

    John Tyndall

  • The molecule of iodine, for example, is monatomic at 1200 C., but becomes diatomic at the ordinary temperature.

  • This information does not inform, since there is a vast number of monatomic alcohols and of every description.

  • The cadmium molecule, as shown by determinations of the density of its vapour, is monatomic.

  • All of them are believed to be monatomic—that is to say, each of their molecules is composed of a single atom.

British Dictionary definitions for monatomic


monoatomic (ˌmɒnəʊəˈtɒmɪk)

adjective chem
  1. (of an element) having or consisting of single atomsargon is a monatomic gas
  2. (of a compound or molecule) having only one atom or group that can be replaced in a chemical reaction
  3. a less common word for monovalent
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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


  1. Occurring as single atoms.
  2. Having one replaceable atom or radical.
  3. Univalent.
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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.