Template:Infobox barium

Barium,  ₅₆Ba

General properties
Name, symbol	barium, Ba
Appearance	silvery gray; with a pale yellow tint
Pronunciation	/ˈbɛriəm/ BAIR-ee-əm
Barium in the periodic table
Sr ↑ Ba ↓ Ra caesium ← barium → lanthanum
Atomic number (Z)	56
Group, block	group 2 (alkaline earth metals), s-block
Period	period 6
Element category	alkaline earth metals
Standard atomic weight (±) (Ar)	137.327(7)
Electron configuration	[Xe] 6s2
per shell	2, 8, 18, 18, 8, 2
Physical properties
Phase	solid
Melting point	1000 K ​(727 °C, ​1341 °F)
Boiling point	2118 K ​(1845 °C, ​3353 °F)
Density near r.t.	3.51 g/cm3
when liquid, at m.p.	3.338 g/cm3
Heat of fusion	7.12 kJ/mol
Heat of vaporization	142 kJ/mol
Molar heat capacity	28.07 J/(mol·K)
vapor pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 911 1038 1185 1388 1686 2170
Atomic properties
Oxidation states	+2, +1 ​(a strongly basic oxide)
Electronegativity	Pauling scale: 0.89
Ionization energies	1st: 502.9 kJ/mol 2nd: 965.2 kJ/mol 3rd: 3600 kJ/mol
Atomic radius	empirical: 222 pm
Covalent radius	215±11 pm
Van der Waals radius	268 pm
Miscellanea
Crystal structure	​body-centered cubic (bcc)
Speed of sound thin rod	1620 m/s (at 20 °C)
Thermal expansion	20.6 µm/(m·K) (at 25 °C)
Thermal conductivity	18.4 W/(m·K)
Electrical resistivity	332 nΩ·m (at 20 °C)
Magnetic ordering	paramagnetic
Young's modulus	13 GPa
Shear modulus	4.9 GPa
Bulk modulus	9.6 GPa
Mohs hardness	1.25
CAS Number	7440-39-3
History
Discovery	Carl Wilhelm Scheele (1772)
First isolation	Humphry Davy (1808)
Most stable isotopes of barium
iso NA half-life DM DE (MeV) DP 130Ba 0.106% (0.5–2.7)×1021 y εε 2.620 130Xe 132Ba 0.101% >3×1020 y (β+β+) 0.846 132Xe 133Ba syn 10.51 y ε 0.517 133Cs 134Ba 2.417% – (SF) <40.520 135Ba 6.592% – (SF) <39.357 136Ba 7.854% – (SF) <38.041 137Ba 11.23% – (SF) <35.722 138Ba 71.7% – (SF) <34.302
Decay modes in parentheses are predicted, but have not yet been observed

References

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