Atomic number 20
Calcium
Alkaline earth metal
In the real world
Quick facts
- Atomic mass
- 40.078
- Group
- 2
- Period
- 4
- State (STP)
- solid
- Electronegativity
- 1.00
- Common ox. states
- +2
Properties
[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 dangerous is it?
A soft silvery metal that reacts with water, though far more gently than sodium, and the metal and its dust can irritate skin.
- CorrosiveImmediate
The fresh metal and its dust are irritating and can burn skin and eyes on contact.
Handled with gloves and goggles so it never touches bare skin or eyes.
- ReactiveImmediate
It reacts with water and moist air, releasing flammable hydrogen and forming a caustic solution. (the pure metal reacts, while the calcium in chalk, bone, and milk is perfectly stable)
Stored dry, away from water, and handled in small pieces.
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
