Nuclides
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Chemical element · Atomic number 20
Calcium (Ca)
Alkaline earth metals · Period 4 · Solid
Element identity
- Atomic number (Z)
- 20
- Symbol
- Ca
- Atomic weight / isotope mass number
- 40.078(4)
- Category
- Alkaline earth metals
- Physical state (reference)
- Solid
- Period
- 4
- Group (reference)
- 2
- Block
- s
Physical properties
- Appearance
- Dull gray, silver, with a pale yellow tint
- Density
- 1.55 g·cm⁻³
- Melting point
- 1115 K / 842 °C / 1548 °F
- Boiling point
- 1757 K / 1484 °C / 2703 °F
- Sublimation point
- Not available
Atomic and material properties
- Electron configuration
- [Ar] 4s²
- Electrons per shell
- K2 L8 M8 N2
- Oxidation states
- 2, 1, −1
- Electronegativity (Pauling)
- 1
- Atomic radius
- 194 pm
- Covalent radius
- 176±10 pm
- Molar ionization energies
- 1st: 589.8 kJ·mol⁻¹ 2nd: 1145.4 kJ·mol⁻¹ 3rd: 4912.4 kJ·mol⁻¹ 4th: 6491 kJ·mol⁻¹ 5th: 8153 kJ·mol⁻¹ 6th: 10,496 kJ·mol⁻¹ 7th: 12,270 kJ·mol⁻¹ 8th: 14,206 kJ·mol⁻¹ 9th: 18,191 kJ·mol⁻¹ 10th: 20,385 kJ·mol⁻¹ 11th: 57,110 kJ·mol⁻¹ 12th: 63,410 kJ·mol⁻¹ 13th: 70,110 kJ·mol⁻¹ 14th: 78,890 kJ·mol⁻¹ 15th: 86,310 kJ·mol⁻¹ 16th: 94,000 kJ·mol⁻¹ 17th: 104,900 kJ·mol⁻¹ 18th: 111,711 kJ·mol⁻¹ 19th: 494,850 kJ·mol⁻¹ 20th: 527,762 kJ·mol⁻¹
- Thermal conductivity
- 201 W·m⁻¹·K⁻¹
- Molar heat capacity
- 25.929 J·mol⁻¹·K⁻¹
- Crystal structure
- Face-centered cubic
- CAS number
- 7440-70-2
Property source: Wikipedia — Calcium, 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.
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