monatomic

American  

[mon-uh-tom-ik] / ˌmɒn əˈtɒm ɪk /

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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monatomic British  

/ ˌmɒnəˈtɒmɪk, ˌmɒnəʊəˈtɒmɪk /

adjective

1. (of an element) having or consisting of single atoms

   argon 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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Other Word Forms

• monatomically adverb

Etymology

Origin of monatomic

First recorded in 1840–50; mon- + atomic

Example Sentences

All monatomic nonmetal ions are anions; examples include the chloride ion, Cl−, the nitride ion, N3−, and the selenide ion, Se2−.

From Textbooks • Feb. 14, 2019

The oxidation number of a monatomic ion is equal to the ion’s charge.

From Textbooks • Feb. 14, 2019

For example, the pure metalloids form covalent crystals like the nonmetals, but like the metals, they generally do not form monatomic anions.

From Textbooks • Feb. 14, 2019

Reinhardt, A. & Doye, J. P. K. Free energy landscapes for homogeneous nucleation of ice for a monatomic water model.

From Nature • Nov. 7, 2017

Atomic and Molecular Heats.—The ideal atomic heat is the thermal capacity of a gramme-atom in the ideal state of monatomic gas at constant volume.

From Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 1 "Calhoun" to "Camoens" by Various