Barium (Ba)
Alkaline earth metal
Barium is a heavy alkaline-earth metal whose insoluble sulfate is opaque to X-rays — the famous “barium meal” that lets doctors image the digestive tract. Its other salts colour fireworks green.
Position on the periodic table
Atomic properties
| Atomic number | 56 |
|---|---|
| Atomic mass | 137.328 amu |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 |
| Noble gas shorthand | [Xe] 6s2 |
| Electrons per shell | 2, 8, 18, 18, 8, 2 |
| Valence electrons (outer shell) | 2 |
| Common oxidation states | +2 |
| Electronegativity (Pauling) | 0.89 |
| Covalent radius (approx.) | 215 pm |
| First ionization energy | 502.9 kJ/mol |
| Electron affinity | 14 kJ/mol |
Physical properties
| State at 25 °C | Solid |
|---|---|
| Density | 3.51 g/cm³ |
| Melting point | 726.85 °C (1000 K) |
| Boiling point | 1844.8 °C (2118 K) |
| Appearance | Not available |
| Radioactive | No |
| Origin | Occurs naturally |
Electron configuration of barium
Barium's ground-state electron configuration is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2, usually shortened to [Xe] 6s2. Its electrons occupy 6 shells (2, 8, 18, 18, 8, 2), placing it in period 6 of the s-block. The 2 outer-shell electrons drive its bonding behaviour. Explore it interactively in the electron configuration calculator.
Uses of barium
- X-ray contrast imaging (barium sulfate)
- Green fireworks
- Drilling mud weighting agent
- Glass and ceramic additives
Biological role: None — soluble barium salts are toxic.
Occurrence: Mined as barite (BaSO₄) and witherite.
Common compounds of barium
BaSO4
Barium sulfate
BaCO3
Barium carbonate
History and discovery
Discovered: 1808 — Carl Wilhelm Scheele. Name origin: From Greek barys, meaning heavy.
Scheele recognised a new “earth” in 1772; Humphry Davy isolated barium metal in 1808.
Safety notes
Soluble barium compounds are poisonous; the insoluble sulfate used in medicine passes through the body unchanged.
Educational context only — always follow your school's laboratory rules and never handle chemicals without proper supervision. See our disclaimer.
Practice questions
Quick practice: Barium
1. What is the chemical symbol of Barium?
2. What is the atomic number of Barium?
3. Which category does Barium belong to?
4. What is the state of Barium at room temperature?
5. Which period of the periodic table is Barium in?
Barium FAQs
What is the atomic number of barium?
Barium's atomic number is 56 — every barium atom has 56 protons in its nucleus.
What is the symbol for barium?
Ba. From Greek barys, meaning heavy.
Is barium a metal, nonmetal, or metalloid?
Barium is classified as a alkaline earth metal.
What state is barium at room temperature?
At about 25 °C, barium is a solid. It melts at 726.85 °C.
How many valence electrons does barium have?
Barium has 2 electrons in its outer shell (shell pattern: 2, 8, 18, 18, 8, 2).
What is barium used for?
Key uses include: x-ray contrast imaging (barium sulfate); green fireworks; drilling mud weighting agent.
Related elements
Keep working with this element
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