Barium (Ba)
Barium is element 56, a alkaline earth metal in period 6, group 2 of the periodic table. At room temperature it is a solid.
Electron configuration [Xe] 6s2
Electrons per shell 2, 8, 18, 18, 8, 2
Barium data
| Atomic number | 56 |
|---|---|
| Symbol | Ba |
| Atomic mass | 137.327 u |
| Category | Alkaline earth metal |
| Group | 2 |
| Period | 6 |
| Block | s |
| State at 25 °C | solid |
| Melting point | 1000 K (726.9 °C) |
| Boiling point | 2143 K (1869.9 °C) |
| Density | 3.51 g/cm³ |
| Electronegativity (Pauling) | 0.89 |
| Atomic radius | 198 pm |
| 1st ionization energy | 503 kJ/mol |
| Electron affinity | -14 kJ/mol |
| Oxidation states | +2 |
| Common ion charge | 2+ |
| Discovered | 1808 |
Orbital diagram
Each box is one orbital holding up to two electrons of opposite spin. Following Hund’s rule, electrons spread out singly across a subshell before pairing.
Work through barium’s configuration and its ions →
Where barium sits
Barium belongs to the alkaline earth metals. Its Pauling electronegativity of 0.89 is among the lowest on the table, so it gives up electrons readily; see the electronegativity chart and periodic trends for context. To use its mass in a calculation, try the molar mass calculator.
Barium FAQ
What is the electron configuration of barium?
Barium (Z = 56) has the configuration 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 6s2. In noble-gas shorthand that is [Xe] 6s2.
How many valence electrons does barium have?
2 (outer shell (n = 6)).
What is the atomic mass of barium?
The standard atomic weight of barium is 137.327 u, so one mole weighs 137.327 g.
Is barium a metal?
Yes. Barium is a alkaline earth metal.
What is the charge of a barium ion?
Barium most commonly forms Ba2+.