Element 20
Calcium (Ca)
Calcium (Ca) is element 20 of the periodic table, an alkaline earth metal in period 4, group 2 (s-block) with an atomic mass of 40.078 and is a solid at standard conditions.
At a glance
- Atomic number
- 20
- Symbol
- Ca
- Atomic mass
- 40.078 u
- Category
- Alkaline earth metals
- Period
- 4
- Group
- 2
- Block
- s-block
- Phase at STP
- solid
Electron structure
- Electron configuration
- 1s2 2s2 2p6 3s2 3p6 4s2
- Shorthand configuration
- [Ar] 4s2
- Electrons per shell
- 2, 8, 8, 2
- Oxidation states
- +1, +2
Physical properties
- Melting point
- 1,115 K (841.85 °C)
- Boiling point
- 1,757 K (1,483.85 °C)
- Density
- 1.54 g/cm³
- Phase
- solid
Atomic properties
- Electronegativity (Pauling)
- 1
- Atomic radius
- 194 pm
- Covalent radius
- 176 pm
- Van der Waals radius
- 231 pm
- First ionization energy
- 590 kJ/mol
- Electron affinity
- 2 kJ/mol
Notable isotopes
| Isotope | Mass | Abundance | Stability |
|---|---|---|---|
| Ca-40 | 39.96259 | 96.94% | Stable |
Common uses
- Bones and teeth
- Cement
- Steel making
- Cheese making
Discovery
- Year
- 1808
- Discovered by
- Humphry Davy
- Country
- England
Frequently asked questions
- Is calcium a metal?
- Yes. Calcium is a metal, classified as an alkaline earth metal on the periodic table.
- How many protons does calcium have?
- Calcium has 20 protons. Its atomic number is 20, which is also the number of electrons in a neutral atom of calcium.
- What group and period is calcium in?
- Calcium is in group 2 and period 4 of the periodic table, in the s-block.
- What is the atomic mass of calcium?
- The atomic mass of calcium is 40.078 u (unified atomic mass units).
Keep exploring
Calcium's row is on the printable element property sheet, and its tile is on the periodic table wall chart - the same numbers as above, laid out for A4 or A3 paper.