Barium
Silvery-white reactive element, belonging to group 2 of the periodic table. Soluble barium compounds are extremely poisonous. Identified in 1774 by Karl Scheele and extracted in 1808 by Humphry Davy.
Gallery
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Physical Propertiesmass · density · phase · crystal
Atomic Mass
137.3270Da
Density
3.6200g/cm³
Phase (STP)
Solid
Melting Point
1000.1K
Boiling Point
2118.2K
Molar Heat
0.2040J/(mol·K)
Crystal Structure
BCC
Lattice Constant
5.020Å
Atomic Radiiatomic · covalent · van der Waals
Atomic (Empirical)
215.00pm
Covalent
196.00pm
Van der Waals
268.00pm
Electronic Propertieselectronegativity · ionization · affinity
Electron Configuration
[Xe] 6s2
Electron Shells
2, 8, 18, 18, 8, 2
Electronegativity
0.89Pauling
Electron Affinity
0.1kJ/mol
1st Ionization Energy
5.2kJ/mol
Oxidation States
+2
Orbital DiagramAufbau · Hund's rule · Pauli exclusion
Full: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 6s2Short: [Xe] 6s2
Ionization Energies (56 known)
Emission Spectrumvisible range · characteristic spectral lines
Abundanceby mass
Log scale · ppm = parts per million by mass
Biological Role
Barium ions are toxic (block potassium channels). Barium sulfate used safely in medical imaging.
Discovery
Discovered By
Sir Humphrey Davy
Named By
—
Year
1808
Nuclear Data
Known Isotopes
42
Stable Isotopes
7
Stable Mass Numbers
130, 132, 134, 135, 136, 137, 138
Natural isotopic abundance (IUPAC recommended values)
Isotopes of Ba42 known
| Nuclide | Z | N | Mass (AMU) | Half-life | Decay | Jπ | Abundance |
|---|---|---|---|---|---|---|---|
| 113Ba | 56 | 57 | 112.957370 | Unknown | p, α | 5/2+ | — |
| 114Ba | 56 | 58 | 113.950718 | 460 ms | β⁺ (1%), β⁺p (0.2%), α (0.009000000000000001%), 12C (0.000034%) | 0+ | — |
| 115Ba | 56 | 59 | 114.947482 | 450 ms | β⁺ (1%), β⁺p (0.15%) | 5/2+ | — |
| 130Bastable | 56 | 74 | 129.906326 | Stable | 2β⁺ | 0+ | 11.0000% |
| 132Bastable | 56 | 76 | 131.905061 | Stable | 2β⁺ | 0+ | 10.0000% |
| 134Bastable | 56 | 78 | 133.904508 | Stable | stable (1%) | 0+ | 242.0000% |
| 135Bastable | 56 | 79 | 134.905688 | Stable | stable (1%) | 3/2+ | 659.0000% |
| 136Bastable | 56 | 80 | 135.904576 | Stable | stable (1%) | 0+ | 785.0000% |
| 137Bastable | 56 | 81 | 136.905827 | Stable | stable (1%) | 3/2+ | 1123.0000% |
| 138Bastable | 56 | 82 | 137.905247 | Stable | stable (1%) | 0+ | 7170.0000% |
| 152Ba | 56 | 96 | 151.955330 | 139 ms | β⁻ (1%), β⁻n | 0+ | — |
| 153Ba | 56 | 97 | 152.960848 | 113 ms | β⁻ (1%), β⁻n, 2n | 5/2- | — |
| 154Ba | 56 | 98 | 153.964659 | 53.0 ms | β⁻ (1%) | 0+ | — |