Atomic number 20
Calcium
Alkaline earth metal
Quick facts
- Atomic mass
- 40.078
- Group
- 2
- Period
- 4
- State (STP)
- solid
- Electronegativity
- 1.00
- Common ox. states
- +2
Properties
Electron configuration
[Ar] 4s²
- Ionization energy
- 589.8 kJ/mol
- Electron affinity
- 2.4 kJ/mol
- Melting point
- 1115.00 K (841.9 °C)
- Boiling point
- 1757.00 K (1483.8 °C)
How it bonds
Calcium forms Ca²⁺ in essentially every common compound (CaCO₃ in limestone, Ca₅(PO₄)₃OH in bone, CaCl₂ for road salt). Less polarizing than Mg²⁺, so its salts are more "purely ionic" — high melting points, conduct when molten.
Where you meet it
- Periodic Quest challengeunlock card