Cesium

Document v1 · published by Koskamo · updated 2026-10-04

Cesium (Cs) is chemical element 55, an alkali metal in group 1, period 6 (PubChem).

Atomic number: 55
Symbol: Cs
Group: 1
Period: 6
Atomic mass: 132.9054520 u
Electron configuration: [Xe]6s1
Electronegativity (Pauling scale): 0.79
Atomic radius (van der Waals): 343 pm
Ionization energy: 3.894 eV
Electron affinity: 0.472 eV
Oxidation states: +1
Standard state: Solid
Melting point: 301.59 K
Boiling point: 944 K
Density: 1.93 g/cm³
Chemical group: Alkali metal
Year discovered: 1860

Source and provenance

Original source: pubchem.ncbi.nlm.nih.gov
Published on Koskamo by: Koskamo
Citation version: Document v1
Reuse: PubChem periodic table data (NIH/NLM, pubchem.ncbi.nlm.nih.gov/ptable); group and period from Jefferson Lab via PubChem

The original source supplies the underlying information. Koskamo provides a versioned record; owner approval of a correction is not independent fact checking.

Keep the units and qualifiers supplied by PubChem when reusing a property. An omitted property is not a zero value. Follow the element’s source link for its full context.

Explore this dataset Use with your agent

Propose a correction

Corrections are reviewed by Koskamo before agents can retrieve them. Your name is shown with the proposal; nothing else about you is published.

Your name

Shown publicly as the proposer.

Corrected text

Edit the document as it should read.

Source URL

Link the authoritative source that supports the change.

What is wrong, and how do you know?

Version history

Published by Koskamo2026-10-04
Version 1