Calcium
Calcium (钙, symbol Ca) is chemical element number 20, an Alkaline Earth in period 4, group 2 of the periodic table, with a standard atomic weight of about 40.078. Fifth most abundant element in Earth's crust. Essential for bones, teeth, and cellular signaling.
Properties
| Atomic number | 20 |
|---|---|
| Symbol | Ca |
| Atomic mass | 40.078 u |
| Category | Alkaline Earth |
| Period | 4 |
| Group | 2 |
| Electron configuration | [Ar] 4s² |
| Electronegativity | 1 |
| Covalent radius | 176 pm |
| Density | 1.54 g/cm³ |
| Melting point | 1115 K |
| Boiling point | 1757 K |
| Discovery | Humphry Davy, 1808 |
Overview
Fifth most abundant element in Earth's crust. Essential for bones, teeth, and cellular signaling. Calcium (symbol Ca) is chemical element number 20, sitting in period 4, group 2 of the periodic table and classed as an Alkaline Earth. As an alkaline-earth metal it is a little less reactive than the alkali metals and occurs in nature mainly within mineral compounds.
Its electron configuration is [Ar] 4s², with 2 electrons in the outer shell, and an electronegativity of about 1 (Pauling). Around 25 °C it is usually a solid; it melts near 1115 K (841.9 °C), boils near 1757 K (1483.9 °C), has a density around 1.54 g/cm³.
In industry and daily life it turns up in Structural / Alloys, Medical / Pharma and Agriculture / Fertiliser. You can explore Ca-containing compounds here such as Ca(OH)₂, CaCO₃ and CaO. It was first described by Humphry Davy in 1808. Browse elements of the same category in the browse view.
Electron shells
Electrons per shell: 2 · 8 · 8 · 2
Main uses
- Structural / Alloys
- Medical / Pharma
- Agriculture / Fertiliser
Hazard
Compounds containing Calcium
Data sources
Atomic mass uses IUPAC (CIAAW) standard atomic weights; the covalent radius is from Cordero et al. (2008). Verify on the RSC Periodic Table, PubChem and Wikipedia. Educational reference only.