Calcium
The metal that builds bones, teeth, and seashells.
Inside the Calcium atom
Switch between Bohr and Quantum Cloud modes to compare a simple teaching model with a more realistic probability-based view, and follow the guided tour to explore the Calcium atom step by step.
Electron configuration
[Ar] 4s2
A neutral Calcium atom has 20 electrons (equal to its proton count). Choosing a different isotope above changes only the neutron count.
Shell distribution
Electrons fill inner shells before outer ones; the outermost (valence) shell drives the element's chemistry.
Physical & atomic properties
- State (room temp)
- Solid
- Melting point
- 1115 K (842 °C)
- Boiling point
- 1757 K (1484 °C)
- Density
- 1.54 g/cm³
- Electronegativity
- 1 Pauling
- Atomic radius
- 180 pm
- 1st ionization energy
- 590 kJ/mol
- Category
- Alkaline earth metals
Discovery & naming
- Discovered
- 1808
- Discovered by
- Humphry Davy
- Origin of name
- Latin 'calx', meaning lime.
Notable uses
Cement, plaster, and the mineral in bones and teeth.
Where Calcium comes from
Stellar fusion and dying stars
Made by silicon and oxygen burning in massive stars. The calcium in your bones passed through one.
Simplified origin map — many elements form through more than one astrophysical pathway.
Summary
- Atomic number
- 20
- Atomic mass
- 40.078
- Category
- Alkaline earth metals
- Group · Period
- 2 · 4
- Block
- s-block
- Shells
- 2 · 8 · 8 · 2