OPOpenPithMake curiosity visibleCHEMISTRY LAB / 02

The Periodic Table

118 elements, raised by their properties.

Click an element to view its atom · drag to orbit · right-drag or two fingers to pan · scroll to zoom

About Caesium

Caesium (IUPAC spelling; also spelled cesium in American English) is a chemical element; it has symbol Cs and atomic number 55. It is a soft, silvery-golden alkali metal with a melting point of 28.5 °C (83.3 °F; 301.6 K), which makes it one of only five elemental metals that are liquid at or near room temperature. Caesium has physical and chemical properties similar to those of rubidium and potassium. It is pyrophoric and reacts with water even at −116 °C (−177 °F). It is the least electronegative stable element, with a value of 0.79 on the Pauling scale. It has only one stable isotope, caesium-133. Caesium is mined mostly from pollucite. Caesium-137, a fission product, is extracted from waste produced by nuclear reactors. It has the largest atomic radius of all elements whose radii have been measured or calculated, at about 260 picometres.

The text above is from the lead of the Wikipedia article “Caesium” (retrieved 2026-11-05), used under CC BY-SA 4.0. Read on Wikipedia · CC BY-SA 4.0

Data and notes

Column height is a linear display mapping; the shortest column is not zero. Data: PubChem, IAEA.

Solid columns are measured, frosted glass is predicted, empty frames have no value.

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