Barium
A dense reactive metal used in medical imaging contrast.
Inside the Barium 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 Barium atom step by step.
Electron configuration
[Xe] 6s2
A neutral Barium atom has 56 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
- 1000 K (727 °C)
- Boiling point
- 2170 K (1897 °C)
- Density
- 3.594 g/cm³
- Electronegativity
- 0.89 Pauling
- Atomic radius
- 215 pm
- 1st ionization energy
- 503 kJ/mol
- Category
- Alkaline earth metals
Discovery & naming
- Discovered
- 1808
- Discovered by
- Humphry Davy
- Origin of name
- Greek 'barys', meaning heavy.
Notable uses
Medical imaging contrast, drilling fluids, and fireworks.
Where Barium comes from
Stellar fusion and dying stars
A classic slow-neutron-capture element, so abundant in dying low-mass stars that they are named for it.
Simplified origin map — many elements form through more than one astrophysical pathway.
Summary
- Atomic number
- 56
- Atomic mass
- 137.33
- Category
- Alkaline earth metals
- Group · Period
- 2 · 6
- Block
- s-block
- Shells
- 2 · 8 · 18 · 18 · 8 · 2