56137.33BaBarium
Barium (Ba) — element 56alkaline earth metal · group 2, period 6
Barium is a chemical element with the symbol Ba and atomic number 56. It is an alkaline earth metal in group 2, period 6 of the periodic table (the s-block), with a standard atomic mass of 137.33 u. At room temperature (25 °C) barium is a solid.
💡 Known for: Barium sulfate makes the digestive tract visible on X-rays, and barium compounds give fireworks a green colour.
# Barium properties
| Symbol | Ba |
|---|---|
| Atomic number | 56 |
| Atomic mass | 137.33 u |
| Category | alkaline earth metal |
| Group | 2 |
| Period | 6 |
| Block | s-block |
| Electron configuration | [Xe] 6s² |
| Full configuration | 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 6s² |
| Electrons per shell | 2, 8, 18, 18, 8, 2 |
| Protons / electrons | 56 / 56 |
| State at 25 °C | solid |
| Melting point | 1000 K (726.9 °C, 1340.3 °F) |
| Boiling point | 2170 K (1896.8 °C, 3446.3 °F) |
| Density | 3.594 g/cm³ |
| Electronegativity (Pauling) | 0.89 |
| First ionization energy | 5.212 eV |
| Atomic radius | 253 pm |
| Discovered | 1808 |
# Electron configuration of barium
The electron configuration of barium is [Xe] 6s², written out in full as 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 6s². Its 56 electrons fill 6 shells as 2, 8, 18, 18, 8, 2, so the outermost shell holds 2 electrons. As a group 2 element, barium has 2 valence electrons.
# Related elements
CsCaesiumprevious elementLaLanthanumnext elementBeBerylliumgroup 2MgMagnesiumgroup 2CaCalciumgroup 2SrStrontiumgroup 2RaRadiumgroup 2
# Barium FAQ
What is the atomic number of barium?
The atomic number of barium is 56: every barium atom has 56 protons in its nucleus. Its symbol is Ba.
What is the atomic mass of barium?
The standard atomic mass of barium is 137.33 u.
What is the electron configuration of barium?
Barium's electron configuration is [Xe] 6s² (1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 6s²), with 2, 8, 18, 18, 8, 2 electrons per shell.
Is barium a metal?
Yes. Barium is an alkaline earth metal, one of the metals.
What is the melting point of barium?
Barium melts at 1000 K (726.9 °C, 1340.3 °F) and boils at 2170 K (1896.8 °C, 3446.3 °F).
What is barium used for / known for?
Barium sulfate makes the digestive tract visible on X-rays, and barium compounds give fireworks a green colour.