Period Definition in Chemistry

Chemistry Glossary Definition of Period

A period is a row of the periodic table.
A period is a row of the periodic table. Lawrence Lawry, Getty Images

Period Definition

In chemistry, the term period refers to a horizontal row of the periodic table. Elements in the same period all have the same highest unexcited electron energy level or same ground state energy level. As you more down the periodic table, there are more elements per element group because the number of electrons allowed per energy sublevel increases.

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Helmenstine, Anne Marie, Ph.D. "Period Definition in Chemistry." ThoughtCo, Feb. 29, 2016, thoughtco.com/definition-of-period-in-chemistry-604599. Helmenstine, Anne Marie, Ph.D. (2016, February 29). Period Definition in Chemistry. Retrieved from https://www.thoughtco.com/definition-of-period-in-chemistry-604599 Helmenstine, Anne Marie, Ph.D. "Period Definition in Chemistry." ThoughtCo. https://www.thoughtco.com/definition-of-period-in-chemistry-604599 (accessed January 16, 2018).