About

Calcium is a reactive, silvery-gray alkaline earth metal. It is the most abundant mineral in the human body, essential for building and maintaining strong bones and teeth. It's also vital for muscle function, nerve transmission, and cell signaling. Commercially, its compounds like limestone (calcium carbonate) are used to make cement and mortar.

Atomic Properties

Atomic Number20

Atomic Weight40.078 u

Neutrons (common)20

Electron Configuration[Ar] 4s²

Full Configuration1s² 2s² 2p⁶ 3s² 3p⁶ 4s²

Electrons per Shell2, 8, 8, 2

Electronegativity1

Electron Affinity2.37 kJ/mol

Oxidation States+2, 0

Covalent Radius176 pm

Van der Waals Radius231 pm

Ionic Radius100 pm

Periodic Table Position

Group2

Period4

BlockS

Chemical SeriesAlkaline earth metals

Physical Properties

State at STPsolid

Appearancedull gray, silvery metal

Crystal Structurefcc

Magnetic Orderingparamagnetic

Speed of Sound3,810 m/s

Poisson Ratio0.31

Thermal Properties

Melting Point1,115 K

Boiling Point1,757 K

Triple Point1,115 K

Thermal Expansion0 1/K

Thermal Conductivity201 W/(m·K)

Specific Heat0.647 J/(g·K)

Molar Heat25.929 J/(mol·K)

Heat of Fusion8.54 kJ/mol

Heat of Vaporization154.7 kJ/mol

Abundance

In Earth's Crust41,500 ppm

In Ocean415 ppm

In Solar System61.1 ppm

In Human Body14,300 ppm

In Universe70 ppm

Discovery

Discovered byHumphry Davy

Discovery Year1,808

Occurrenceprimordial

CAS Number7440-70-2

Electron Configuration

Energy

↿⇂

Isotopes of Calcium

Symbol ▲	Mass (u) ▲	Abundance ▲	Half-life ▲	Decay Mode ▲
⁴⁰Ca	39.962590	96.941%	Stable	Stable
⁴¹Ca	40.962278	Trace	99.4 ky	Electron Capture
⁴²Ca	41.958618	0.647%	Stable	Stable
⁴³Ca	42.958766	0.135%	Stable	Stable
⁴⁴Ca	43.955481	2.086%	Stable	Stable
⁴⁵Ca	44.956184	—	162.61 d	Beta Minus Decay
⁴⁶Ca	45.953690	0.004%	Stable	Stable
⁴⁸Ca	47.952534	0.187%	56 Ey	Double Beta Minus Decay

Interactive Visualization

Explore the 3D Bohr model of Calcium in our interactive viewer.

View 3D Model of Calcium