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Pronunciation | (BAIR-ee-əm) |
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Appearance | silvery gray; with a pale yellow tint[1] |
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| 137.327(7)[2] |
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Group | group 2 (alkaline earth metals) |
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Period | period 6 |
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Block | s-block |
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Electron configuration | [Xe] 6s2 |
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Electrons per shell | 2, 8, 18, 18, 8, 2 |
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Phase at STP | solid |
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Melting point | 1000 K (727 °C, 1341 °F) |
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Boiling point | 2118 K (1845 °C, 3353 °F) |
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Density (near r.t.) | 3.51 g/cm3 |
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when liquid (at m.p.) | 3.338 g/cm3 |
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Heat of fusion | 7.12 kJ/mol |
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Heat of vaporization | 142 kJ/mol |
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Molar heat capacity | 28.07 J/(mol·K) |
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Vapor pressure
P (Pa) |
1 |
10 |
100 |
1 k |
10 k |
100 k |
at T (K) |
911 |
1038 |
1185 |
1388 |
1686 |
2170 |
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Oxidation states | +1, +2 (a strongly basic oxide) |
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Electronegativity | Pauling scale: 0.89 |
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Ionization energies | - 1st: 502.9 kJ/mol
- 2nd: 965.2 kJ/mol
- 3rd: 3600 kJ/mol
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Atomic radius | empirical: 222 pm |
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Covalent radius | 215±11 pm |
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Van der Waals radius | 268 pm |
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Spectral lines of barium |
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Natural occurrence | primordial |
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Crystal structure | body-centered cubic (bcc) |
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Speed of sound thin rod | 1620 m/s (at 20 °C) |
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Thermal expansion | 20.6 µm/(m⋅K) (at 25 °C) |
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Thermal conductivity | 18.4 W/(m⋅K) |
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Electrical resistivity | 332 nΩ⋅m (at 20 °C) |
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Magnetic ordering | paramagnetic[3] |
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Molar magnetic susceptibility | +20.6·10−6 cm3/mol[4] |
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Young's modulus | 13 GPa |
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Shear modulus | 4.9 GPa |
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Bulk modulus | 9.6 GPa |
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Mohs hardness | 1.25 |
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CAS Number | 7440-39-3 |
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Discovery | Carl Wilhelm Scheele (1772) |
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First isolation | Humphry Davy (1808) |
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Main isotopes[5] |
Decay |
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abundance |
half-life (t1/2) |
mode |
product |
130Ba |
0.11% |
(0.5–2.7)×1021 y |
εε |
130Xe |
132Ba |
0.1% |
stable |
133Ba |
synth |
10.51 y |
ε |
133Cs |
134Ba |
2.42% |
stable |
135Ba |
6.59% |
stable |
136Ba |
7.85% |
stable |
137Ba |
11.2% |
stable |
138Ba |
71.7% |
stable |
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Category: Barium | references |