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caesium
Image: Wikimedia Commons

caesium

Chemical element with symbol Cs and atomic number 55

Chemical elementchemical elementlithophile elementactive metalQ1108

Also known as Cs · cesium · cæsium · 55Cs · element 55

Symbol
Atomic number
Mass
Melting point
  • 301.66 K
Boiling point
  • 941.4 K
Density
  • 1,900 kg/m³
Discovered by
Discovered

Overview

All data

144 statements · 25% with external sources · numbers in brackets are citations

Subclass of
Location of discovery
Canonical SMILES
Formula
Standard molar entropy
Has characteristic
Named after
Part of
Oxidation state
  • 1
  • -1
Ionization energy
  • 375.7 kilojoule per mole
  • 2,234.3 kilojoule per mole
  • 3,400 kilojoule per mole
Mohs' hardness
  • 0.2
Unicode character
Electronegativity
  • 0.79
Different from
Ionic radius
  • 1.67 ångström charge number: 1 · coordination number: 6
  • 1.74 ångström charge number: 1 · coordination number: 8
  • 1.81 ångström charge number: 1 · coordination number: 10
  • 1.88 ångström charge number: 1 · coordination number: 12
Electron configuration
  • [Xe] 6s¹
  • 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s¹
Thermal conductivity
  • 36 watt per metre kelvin
Electrical conductivity
  • 4,760,000 siemens per metre
Electrical resistivity
  • 2.05e-7 ohm metre
Standard enthalpy of formation
  • 76.5 kilojoule per mole state of matter: gas
  • 2.09 kilojoule per mole state of matter: liquid
Linear thermal expansion coefficient
  • 92.6 micrometre per metre kelvin temperature: 20°C
IPA transcription
Crystal system
Atomic radius
  • 260 picometre
Covalent radius
  • 244 picometre

On other databases

77 identifiers linking caesium across the web's reference databases