Ca
Calcium
Element 20 · Alkaline earth metal
Calcium (Ca)
Calcium is a reactive alkaline earth metal and the most abundant metal in the human body, where it builds bones and teeth.
- Alkaline earth metal
- Period 4
- Group 2
- s-block
- solid at room temperature
Key properties
- Atomic mass
- 40.08
- u
- Electron configuration
- [Ar] 4s2
- Melting point
- 841.9 °C
- 1,115 K
- Boiling point
- 1,483.9 °C
- 1,757 K
- Density
- 1.54 g/cm³
- Electronegativity
- 1
- Pauling
- Atomic radius
- 231 pm
- van der Waals
- 1st ionisation energy
- 6.113 eV
Compare with every element:Electronegativity chartAtomic radius chartIonisation energy chartDensity chart of the elementsMelting point chartElectron configuration chart
Did you know?
Notable facts about calcium
- 01
About 99% of the body’s calcium is stored in bones and teeth.
- 02
Limestone, marble and chalk are all forms of calcium carbonate.
- 03
Calcium ions trigger every heartbeat and muscle contraction.
Applications
What is calcium used for?
- Cement and concrete
- Dietary supplements
- Reducing agent for metals
- Plaster and drywall (gypsum)
History
Discovery & name origin
Atomic structure
Atomic properties
Atomic structure
Atomic properties
- Atomic number
- 20
- Atomic mass
- 40.08 u
- 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
- Electronegativity (Pauling)
- 1
- Electron affinity
- —
- Atomic radius (van der Waals)
- 231 pm
- Stable isotopes
- 5
Oxidation states
Highlighted: common oxidation states (+2).
Successive ionisation energies
Energy to remove each electron in turn (kJ/mol). Big jumps show where a new, inner shell begins.
- 1st589.8
- 2nd1,145.4
- 3rd4,912.4
- 4th6,491
- 5th8,153
- 6th10,496
- 7th12,270
- 8th14,206
Physical
Physical properties & colour
Physical
Physical properties & colour
- State at 20 °C
- Solid
- Melting point
- 1,115 K · 841.9 °C · 1,547.3 °F
- Boiling point
- 1,757 K · 1,483.9 °C · 2,702.9 °F
- Density
- 1.54 g/cm³
- Molar heat capacity
- 25.929 J/(mol·K)
- Appearance
- —
- CPK model colour
- Copied
The CPK colour is the convention used for this element’s atoms in molecular models.
FAQ
Calcium questions
What is Ca on the periodic table?
Ca is the symbol for calcium, element 20 on the periodic table. It sits in group 2, period 4, in the alkaline earth metal category, and has an atomic mass of 40.08.
What is the atomic number of calcium?
Calcium has atomic number 20, so every calcium atom has 20 protons in its nucleus. Its symbol is Ca and its atomic mass is 40.08.
Who discovered calcium?
Calcium was discovered by Humphry Davy in 1808 (England). The name comes from Latin calx, “lime”.
What is calcium used for?
Calcium is used for: cement and concrete; dietary supplements; reducing agent for metals; plaster and drywall (gypsum).
Is calcium a metal?
Yes. Calcium is a alkaline earth metal, one of the metallic elements.
What is the electron configuration of calcium?
The electron configuration of calcium is [Ar] 4s2. Its 20 electrons are arranged in shells as 2, 8, 8, 2.