Barium

Barium, ₅₆Ba

Barium
Pronunciation	/ˈbɛəriəm/ ​(BAIR-ee-əm)
Appearance	silvery gray; with a pale yellow tint[1]
Standard atomic weight Ar°(Ba)
	137.327±0.007[2] 137.33±0.01 (abridged)[3]
Barium in the periodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson Sr ↑ Ba ↓ Ra caesium ← barium → lanthanum
Atomic number (Z)	56
Group	group 2 (alkaline earth metals)
Period	period 6
Block	s-block
Electron configuration	[Xe] 6s2
Electrons per shell	2, 8, 18, 18, 8, 2
Physical properties
Phase at STP	solid
Melting point	1000 K ​(727 °C, ​1341 °F)
Boiling point	2118 K ​(1845 °C, ​3353 °F)
Density (at 20° C)	3.594 g/cm3 [4]
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	common: +2 +1?
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
Spectral lines of barium
Other properties
Natural occurrence	primordial
Crystal structure	​body-centered cubic (bcc) (cI2)
Lattice constant	a = 502.5 pm (at 20 °C)[4]
Thermal expansion	20.47×10−6/K (at 20 °C)[4]
Thermal conductivity	18.4 W/(m⋅K)
Electrical resistivity	332 nΩ⋅m (at 20 °C)
Magnetic ordering	paramagnetic[5]
Molar magnetic susceptibility	+20.6×10−6 cm3/mol[6]
Young's modulus	13 GPa
Shear modulus	4.9 GPa
Bulk modulus	9.6 GPa
Speed of sound thin rod	1620 m/s (at 20 °C)
Mohs hardness	1.25
CAS Number	7440-39-3
History
Discovery	Carl Wilhelm Scheele (1772)
First isolation	Humphry Davy (1808)
Isotopes of barium v e
Main isotopes[7] Decay 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
Category: Barium view talk edit | references

Barium is a chemical element; it has symbol Ba and atomic number 56. It is the fifth element in group 2 and is a soft, silvery alkaline earth metal. Because of its high chemical reactivity, barium is never found in nature as a free element.

The most common minerals of barium are barite (barium sulfate, BaSO₄) and witherite (barium carbonate, BaCO₃). The name barium originates from the alchemical derivative "baryta", from Greek βαρὺς (barys), meaning 'heavy'. Baric is the adjectival form of barium. Barium was identified as a new element in 1772, but not reduced to a metal until 1808 with the advent of electrolysis.

Barium has few industrial applications. Historically, it was used as a getter for vacuum tubes and in oxide form as the emissive coating on indirectly heated cathodes. It is a component of YBCO (high-temperature superconductors) and electroceramics, and is added to steel and cast iron to reduce the size of carbon grains within the microstructure. Barium compounds are added to fireworks to impart a green color. Barium sulfate is used as an insoluble additive to oil well drilling fluid. In a purer form it is used as X-ray radiocontrast agents for imaging the human gastrointestinal tract. Water-soluble barium compounds are poisonous and have been used as rodenticides.