55Solid
Cs 132.905 Atomic mass · uAlkali metals
Cesium
Caesium or cesium is a chemical element with symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of 28 °C (82 °F), which makes it one of only five elemental metals that are liquid at or near room temperature. Caesium is an alkali metal and has physical and chemical properties similar to those of rubidium and potassium.
Discovery 1860 (Robert Bunsen)
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Physical properties
Values for the element in its standard state.
- Density
- 1.879g/cm³
- Melting point
- 302K
- Boiling point
- 944K
- Atomic radius
- 225pm
- Bonding type
- Metallic
- Molar heat
- 32.21J/(mol·K)
Inside the atom
Electron arrangement and the energy behind its behavior.
Full electron configuration
1s, 2 electrons; 2s, 2 electrons; 2p, 6 electrons; 3s, 2 electrons; 3p, 6 electrons; 3d, 10 electrons; 4s, 2 electrons; 4p, 6 electrons; 4d, 10 electrons; 5s, 2 electrons; 5p, 6 electrons; 6s, 1 electrons;
[Xe] represents 54 core electrons. The full view shows them explicitly.
55 electrons Orbital order preserved from source
- Electronegativity
- 0.79Pauling scale
- First ionization energy
- 376kJ/mol
- Electron affinity
- 46kJ/mol
- Van der Waals radius
- Not available
Cs CesiumAtomic number 55
376kJ/mol
Atomic numberGaps indicate unavailable data
About cesium
- Appearance
- Silvery gold
- Discovery
- 1860 (Robert Bunsen)
- Data source
- Read the reference
A missing value means it is unavailable in this reference dataset. Values can vary with measurement method and conditions.