Calcium (Ca)
Calcium (Ca) is element 20, an alkaline earth metal. Atomic mass 40.078, configuration [Ar] 4s². Properties, isotopes, oxidation states, uses and history, with an interactive 3D atom model.
Key facts
| Atomic number | 20 |
|---|---|
| Symbol | Ca |
| Standard atomic weight | 40.078(4) |
| Category | Alkaline Earth Metal |
| Group | 2 |
| Period | 4 |
| State at room temperature | Solid |
| Electron configuration | [Ar] 4s² |
| Valence electrons | 2 |
| Common oxidation states | +2 |
| Common ions | Ca²⁺ |
| Electronegativity (Pauling) | 1 |
| First ionization energy | 590 kJ/mol |
| Electron affinity | 2.369 kJ/mol |
| Atomic radius | 194 pm |
| Density | 1.54 g/cm³ |
| Melting point | 842°C |
| Boiling point | 1484°C |
| Specific heat | 0.647 J/(g·°C) |
Natural isotopes
- Ca-40: Stable (96.94%)
- Ca-42: Stable (0.647%)
- Ca-43: Stable (0.135%)
- Ca-44: Stable (2.086%)
- Ca-48: Radioactive (0.187%)
Common uses
- Cement
- Steelmaking (Desulfurization)
- Dietary supplements
Where it matters
- Construction (Concrete/Cement chemistry)
- Human Anatomy (Bones/Teeth structure)
Hazards
- Reacts with water (slowly compared to Na/K)
History
| Discovered | 1808 |
|---|---|
| Discovered by | Humphry Davy |
| Name | From Latin calx (lime) |