Nuclides
About the app ↗
Chemical element · Atomic number 55
Cesium (Cs)
Alkali metals · Period 6 · Solid
Element identity
- Atomic number (Z)
- 55
- Symbol
- Cs
- Atomic weight / isotope mass number
- 132.905 451 96(6)
- Category
- Alkali metals
- Physical state (reference)
- Solid
- Period
- 6
- Group (reference)
- 1
- Block
- s
Physical properties
- Appearance
- Silvery gold
- Density
- 1.93 g·cm⁻³
- Melting point
- 301.7 K / 28.5 °C / 83.3 °F
- Boiling point
- 944 K / 671 °C / 1240 °F
- Sublimation point
- Not available
Atomic and material properties
- Electron configuration
- [Xe] 6s¹
- Electrons per shell
- K2 L8 M18 N18 O8 P1
- Oxidation states
- 1, −1
- Electronegativity (Pauling)
- 0.79
- Atomic radius
- 298 pm
- Covalent radius
- 244±11 pm
- Molar ionization energies
- 1st: 375.7 kJ·mol⁻¹ 2nd: 2234.3 kJ·mol⁻¹ 3rd: 3400 kJ·mol⁻¹
- Thermal conductivity
- 35.9 W·m⁻¹·K⁻¹
- Molar heat capacity
- 32.210 J·mol⁻¹·K⁻¹
- Crystal structure
- Body-centered cubic
- CAS number
- 7440-46-2
Property source: Wikipedia — Cesium, adapted from the Nuclides App snapshot. Quoted conditions and qualifiers are retained.
Sources and interpretation
Snapshot exported 24 October 2026 from the element assets used by Nuclides. Properties are a reference compilation, not a new evaluation. Missing values are shown as “Not available”. Density and phase depend on temperature, pressure and allotrope; retained conditions are part of the quoted property.
Atomic weight is dimensionless. Parentheses give uncertainty in the last quoted digits. A single integer in square brackets is an isotope mass number, not a standard atomic weight. The snapshot can differ from current evaluations; consult CIAAW standard atomic weights and the IUPAC periodic table for current values and conventions.
Element properties in the App snapshot are adapted from Wikipedia. Each element page links to its source article; text adaptations are available under CC BY-SA 4.0. No third-party images are included.
Go from elements to nuclear data
Keep Nuclides on your phone.
Explore connected element and nuclide references, decay chains and calculators in the app. See each store for pricing and in-app purchases.
