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Barium |
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Pronunciation | (BAIR-ee-əm) |
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Appearance | sillery gray; wi a fauch yellae tint[1] |
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Standard atomic weight Ar, std(Ba) | 7002137327000000000♠137.327(7)[2] |
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Barium in the periodic cairt |
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Atomic nummer (Z) | 56 |
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Group | group 2 (alkaline yird metals) |
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Period | period 6 |
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Block | s-block |
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Element category | Alkaline earth metal |
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Electron confeeguration | [Xe] 6s2 |
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Electrons per shell | 2, 8, 18, 18, 8, 2 |
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Pheesical properties |
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Phase at STP | solit |
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Meltin pynt | 1000 K (727 °C, 1341 °F) |
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Bylin pynt | 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 o fusion | 7.12 kJ/mol |
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Heat o vapourisation | 142 kJ/mol |
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Molar heat capacity | 28.07 J/(mol·K) |
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Vapour pressur
P (Pa) |
1 |
10 |
100 |
1 k |
10 k |
100 k |
at T (K) |
911 |
1038 |
1185 |
1388 |
1686 |
2170 |
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Atomic properties |
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Oxidation states | +1, +2 strangly basic |
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Electronegativity | Pauling scale: 0.89 |
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Ionisation 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 o barium |
Ither properties |
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Naitural occurrence | primordial |
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Creestal structur | body-centred cubic (bcc) |
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Speed o soond 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 orderin | paramagnetic[3] |
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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 haurdness | 1.25 |
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CAS Nummer | 7440-39-3 |
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History |
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Diskivery | Carl Wilhelm Scheele (1772) |
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First isolation | Humphry Davy (1808) |
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Main isotopes o barium |
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Isotope |
Abundance |
Hauf-life (t1/2) |
Decay mode |
Product |
130Ba |
0.106% |
(0.5–2.7)×1021 y |
εε |
130Xe |
132Ba |
0.101% |
>3×1020 y |
(β+β+) |
132Xe |
133Ba |
syn |
10.51 y |
ε |
133Cs |
134Ba |
2.417% |
– |
(SF) |
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135Ba |
6.592% |
– |
(SF) |
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136Ba |
7.854% |
– |
(SF) |
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137Ba |
11.23% |
– |
(SF) |
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138Ba |
71.7% |
– |
(SF) |
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Decay modes in parentheses is predictit, but hisnae yet been observed |
| references |