Calcium (Ca)

Dull gray metal

Calcium is the metal that builds your bones and teeth, and it's the fifth most abundant element on Earth, and with a filled 4s² shell, calcium readily forms Ca²⁺ ions essential for muscle contraction, nerve signaling, and blood clotting. It is the most abundant metal in the human body at about 1 kg.

Key metrics

Density1.54g/cm³

Melting point1,115K

Boiling point1,757K

Electronegativity1Pauling

Discovery

1808discovered

Discovered by: Humphry Davy
Reactivity profile: Reacts with Water Slowly
Reactivity: Medium
Bonding: Metallic

Electron configuration

\textcolor{#6b7280}{[Ar]}\; \textcolor{#ef4444}{4_{s}^{2}}

[Ar] 4s2

Wave function

\Psi_{\text{Ca}} \approx \frac{1}{\sqrt{20!}} \det \left| \chi_1(\mathbf{r}_1) \dots \chi_{20}(\mathbf{r}_{20}) \right|

Probability density $|\Psi|^2$ across the Ca valence shell.

Crystal structure

Face-Centered Cubic

Lattice constantsa = 1.00

Cell anglesα = β = γ = 90°

Coordination number12

Atoms per cell4

Atomic packing factor0.74

Physical properties

Atomic radius: 197 pm
Ionization energy: 590 kJ/mol
Electron affinity: 2.4 kJ/mol
Crystal structure: Face-centered cubic (fcc)

Oxidation states

Acid/base

Basic

Strongly acidicStrongly basic

State at 25 °CSolid

1115 K1757 K298 K

Emission spectrum

3 transitions

380450500550600650700780

VioletBlueGreenYellowRed

422.7nmCa I (blue)Violet100%

558.9nmCa I (green)Green40%

616.2nmCa I (orange)Orange50%

Dominant line 422.7 nmRange 423–616 nmTransitions 3