2040.078CaCalcium
Calcium (Ca) — element 20alkaline earth metal · group 2, period 4
Calcium is a chemical element with the symbol Ca and atomic number 20. It is an alkaline earth metal in group 2, period 4 of the periodic table (the s-block), with a standard atomic mass of 40.078 u. At room temperature (25 °C) calcium is a solid.
💡 Known for: Builds bones and teeth, and is found in limestone, chalk, marble and cement.
# Calcium properties
| Symbol | Ca |
|---|---|
| Atomic number | 20 |
| Atomic mass | 40.078 u |
| Category | alkaline earth metal |
| Group | 2 |
| Period | 4 |
| Block | s-block |
| Electron configuration | [Ar] 4s² |
| Full configuration | 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² |
| Electrons per shell | 2, 8, 8, 2 |
| Protons / electrons | 20 / 20 |
| State at 25 °C | solid |
| Melting point | 1115 K (841.9 °C, 1547.3 °F) |
| Boiling point | 1757 K (1483.8 °C, 2702.9 °F) |
| Density | 1.54 g/cm³ |
| Electronegativity (Pauling) | 1 |
| First ionization energy | 6.113 eV |
| Atomic radius | 194 pm |
| Discovered | 1808 |
# Electron configuration of calcium
The electron configuration of calcium is [Ar] 4s², written out in full as 1s² 2s² 2p⁶ 3s² 3p⁶ 4s². Its 20 electrons fill 4 shells as 2, 8, 8, 2, so the outermost shell holds 2 electrons. As a group 2 element, calcium has 2 valence electrons.
# Related elements
KPotassiumprevious elementScScandiumnext elementBeBerylliumgroup 2MgMagnesiumgroup 2SrStrontiumgroup 2BaBariumgroup 2RaRadiumgroup 2
# Calcium FAQ
What is the atomic number of calcium?
The atomic number of calcium is 20: every calcium atom has 20 protons in its nucleus. Its symbol is Ca.
What is the atomic mass of calcium?
The standard atomic mass of calcium is 40.078 u.
What is the electron configuration of calcium?
Calcium's electron configuration is [Ar] 4s² (1s² 2s² 2p⁶ 3s² 3p⁶ 4s²), with 2, 8, 8, 2 electrons per shell.
Is calcium a metal?
Yes. Calcium is an alkaline earth metal, one of the metals.
What is the melting point of calcium?
Calcium melts at 1115 K (841.9 °C, 1547.3 °F) and boils at 1757 K (1483.8 °C, 2702.9 °F).
What is calcium used for / known for?
Builds bones and teeth, and is found in limestone, chalk, marble and cement.