020Alkaline earth metal · Group 2 · Period 4
Calcium
Calcium (Ca) is element 20, a alkaline earth metal in the s-block — group 2, period 4. It is a solid at room temperature with 4 electron shells (2, 8, 8, 2) and an atomic mass of 40.0784 u.
- Atomic mass
- 40.08 u
- Phase · STP
- solid
- Melting
- 1115 K · 842 °C
- Boiling
- 1757 K · 1484 °C
- Electronegativity
- 1
- Density
- 1.55 g/cm³
Photograph — Jurii, CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons, source: https://images-of-elements.com/calcium.php
Emission spectrum
The visible light Calcium emits when energised — its unique spectral fingerprint.
Identity
- Atomic number
- 20
- Standard atomic weight
- 40.08 u
- Category
- Alkaline earth metal
- Group
- 2 · Alkaline earth metals
- Period
- 4
- Block
- s-block
- Oxidation states
- +2
Physical properties
- Melting point
- 1115 K · 842 °C
- Boiling point
- 1757 K · 1484 °C
- Density
- 1.55 g/cm³
- Molar heat capacity
- 25.929 J/(mol·K)
- Atomic radius
- 231 pm
- Electron affinity
- 2.37 kJ/mol
Atomic structure
20protons
20neutrons
20electrons
2valence e⁻
- Noble-gas notation
- [Ar] 4s2
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s2
- Electrons per shell
- 2, 8, 8, 2
Periodic trends
Where Calcium ranks across all 118 elements.
Ionization energies
Energy to remove each successive electron (kJ/mol).
589.81
1.1k2
4.9k3
6.5k4
8.2k5
10.5k6
12.3k7
14.2k8
18.2k9
20.4k10
Successive ionization energies (kJ/mol, log scale).
Discovery
- Discovered
- Ancient
- Discovered by
- Humphry Davy
- Named by
- —
- Appearance
- —