cesium

or cae·si·um

[ see-zee-uhm ]

/ ˈsi zi əm /

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noun

a rare, highly reactive, soft, metallic element of the alkali metal group, used chiefly in photoelectric cells. Symbol: Cs; atomic weight: 132.905; atomic number: 55; specific gravity: 1.9 at 20°C; melts at 28.5°C.

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Origin of cesium

1930–35; <New Latin, special use of Latin caesium, neuter of caesius bluish-grey; see -ium

Words nearby cesium

Cesarean, cesarean section, cesarevitch, Cesca chair, Cesena, cesium, cesium 137, České Budějovice, Československo, Cesky terrier, cespitose

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2022

How to use cesium in a sentence

After these fuel assemblies work for a couple of years in the reactor core, they accumulate an enormous amount of fission products which are very radioactive, such as iodine, cesium, and strontium.
What is the risk of a nuclear accident in Ukraine? A radiation expert speaks from Kyiv.|Jessica Hamzelou|March 25, 2022|MIT Technology Review
Scientists delved into atoms of the element cesium, where a process called the hyperfine transition emits and absorbs microwaves, which scientists could time very precisely with the help of a vibrating quartz crystal.
The most precise atomic clocks ever are proving Einstein right—again|Rahul Rao|February 17, 2022|Popular-Science
So in terms of metallic character, cesium and fluorine are polar opposites.
Explainer: What is a metal?|Katie Grace Carpenter|January 12, 2022|Science News For Students
The levels of radioactive cesium and potassium were elevated, and the source was unmistakable.
Radioactive Tuna Won’t Kill You—but Should We Be Concerned About Mercury?|Daniel Stone|May 30, 2012|DAILY BEAST

Even at the Chernobyl meltdown in 1986, he pointed out, cesium and iodine were the problem.
The Toxic Fuel Inside Japan's Nuclear Plant|Eve Conant|March 15, 2011|DAILY BEAST
Of particular concern: cesium-137 in the pool, at levels Alvarez estimates at 20 million to 50 million curies.
The Japan Nuke Problem No One's Talking About|Sharon Begley|March 14, 2011|DAILY BEAST
It was established that strontium-90 and cesium-137, important in fallout on land, enter the marine cycles only in minute amounts.
Atoms, Nature, and Man|Neal O. Hines

British Dictionary definitions for cesium

cesium

/ (ˈsiːzɪəm) /

noun

the usual US spelling of caesium

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

Scientific definitions for cesium

cesium

[ sē′zē-əm ]

A soft, ductile, silvery-white element of the alkali group. It is liquid at room temperature and is the most reactive of all metals. Cesium is used to make photoelectric cells, electron tubes, and atomic clocks. Atomic number 55; atomic weight 132.905; melting point 28.5°C; boiling point 690°C; specific gravity 1.87; valence 1. See Periodic Table.