Caesium (Cs)

About Caesium

Caesium is a chemical element with the symbol Cs and atomic number 55, meaning every atom has 55 protons in its nucleus. It is classed as Alkali metal and is a solid at room temperature. Its atomic mass is about 132.905 atomic mass units (u).

On the periodic table, Caesium sits in group 1, period 6, which determines how many electron shells it has and how it tends to react with other elements.

Uses of Caesium

In daily life and industry, Caesium is used for Atomic clocks. These uses are closely tied to the typical properties of elements in the Alkali metal category.

Electron Structure of Caesium

Using a simplified electron shell model (at most 2 electrons in the first shell, 8 in the second, 18 in the third, and so on), Caesium has 4 electron shells, with an approximate arrangement of 2, 8, 18, 27 electrons from the innermost shell to the outermost. This is a simplified learning model, not the full electron configuration that accounts for the s, p, d and f subshells.

Explore Other Elements

Want to see another element or try the element symbol quiz? Go back to the Interactive Periodic Table to explore all 118 chemical elements.

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