Chemical element · Atomic number 55
Cesium
Cesium in the periodic table: atomic number 55, electron configuration, atomic mass, physical data, oxidation states, media credit and visible sources.
Alkali metal
solid
132.9054520 u
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Atomic classification
Shell occupancy
Cesium in the Bohr shell model
This shows the electron distribution of the neutral atom in a simplified shell model.
- K · n=1
- 2 electrons
- L · n=2
- 8 electrons
- M · n=3
- 18 electrons
- N · n=4
- 18 electrons
- O · n=5
- 8 electrons
- P · n=6
- 1 electron
- Electron configuration
- [Xe]6s1
- Electrons per shell
- 2 · 8 · 18 · 18 · 8 · 1
- Group
- 1
- Period
- 6
- Block
- S
- Element category
- Alkali metal
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Physical and chemical properties
- Atomic mass
- 132.9054520 u
- Standard state
- solid
- Density
- 1.93 g/cm³
- Melting point
- 301.59 K
- Boiling point
- 944 K
- Electronegativity
- 0.79 (Pauling)
- First ionisation energy
- 3.894 eV
- Oxidation states
- +1
- Discovery
- 1860
Safety and periodic classification
Safety
Safe handling cannot be inferred from Cesium's position in the periodic table alone. Laboratory, classroom and disposal decisions must follow the documentation for the exact material and its safety data sheet.
Position and comparison
Cesium is in period 6, group 1 and the S block. Its direct neighbours by atomic number are Xenon and Barium. The recorded Pauling electronegativity is 0.79. Periodic trends are compared only through the separately sourced neighbouring values.
Sources and scope
PubChem attributes element data to sources including IUPAC, NIST and IAEA. Quanta stores the referenced snapshot locally and leaves unknown values unavailable.