Barium (Ba): Electron Configuration, Properties and Uses
Barium (Ba): Electron Configuration, Properties and Uses
Electron configuration [Xe] 6s2 · group 2 · period 6 · Ar 137.33
Barium data
- Atomic number
- 56
- Relative atomic mass
- 137.33
- Group
- 2
- Period
- 6
- Block
- s
- Category
- Alkaline earth metal
- Electron configuration
- [Xe] 6s2
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2
- Electrons per shell
- 2, 8, 18, 18, 8, 2 (K L M N O P)
- Valence electrons
- 2
- Electronegativity (Pauling)
- 0.89
- First ionisation energy
- 5.212 eV
- Atomic radius (van der Waals)
- 268 pm
- State at room temperature
- Solid
- Melting point
- 727 °C
- Boiling point
- 1897 °C
- Density
- 3.62 g/cm³
- Common oxidation states
- +2
- Discovered
- 1808
Source: PubChem (NIH, accessed 13 Nov 2026); atomic mass: IUPAC standard atomic weight.
Electron shell diagram
K 2 · L 8 · M 18 · N 18 · O 8 · P 2
Orbital diagram (outer electrons)
About barium
Barium, symbol Ba, is element number 56 in the periodic table. It is an alkaline earth metal in group 2, period 6, s-block. Barium was first discovered in 1808. Barium is a solid at room temperature, melting at 727 °C and boiling at 1897 °C.
Barium electron configuration
The electron configuration of barium is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2, or in short [Xe] 6s2. Its electrons occupy 6 shells: K = 2, L = 8, M = 18, N = 18, O = 8, P = 2. Barium has 2 valence electrons in the P shell (6s2), which is why it sits in group 2. When it forms cations, electrons leave the outermost subshell first: Ba2+ = [Xe] (like xenon).
Filling order: 1s2(2) → 2s2(4) → 2p6(10) → 3s2(12) → 3p6(18) → 4s2(20) → 3d10(30) → 4p6(36) → 5s2(38) → 4d10(48) → 5p6(54) → 6s2(56)
Uses of barium
Well-known applications of barium include barium sulfate for gastrointestinal X-ray contrast and drilling mud, and green fireworks. For research and analysis you can browse barium compounds in the AMI Scientific catalogue.
Safety
Soluble barium compounds such as BaCl2 are toxic. Barium sulfate is safe as a contrast agent because it is almost insoluble. Always read the safety data sheet (SDS) before working with a chemical.
Other elements in group 2
Frequently asked questions
What is the electron configuration of barium?
The electron configuration of barium (Ba, atomic number 56) is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2, or [Xe] 6s2 in short. By shell: 2, 8, 18, 18, 8, 2.
How many valence electrons does barium have?
Barium has 2 valence electrons.
Which group and period is barium in?
Barium is in group 2, period 6, s-block.
What is the atomic mass of barium?
The relative atomic mass of barium is 137.33. Use it to calculate molar mass with the molar mass calculator.
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