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Barium (Ba)

Barium is a chemical element of the periodic table with chemical symbol Ba and atomic number 56 with an atomic weight of 137.328 u and is classed as alkaline earth metal and is part of group 2 (alkaline earth metal). Barium is solid at room temperature.

Barium in the periodic table

Atomic number56
Group2 (Alkaline earth metal)
ClassificationAlkaline Earth Metal
Color Silver
Number of protons56 p+
Number of neutrons81 n0
Number of electrons56 e-
From Wikipedia, the free encyclopediaBarium is a chemical element with symbol Ba and atomic number 56. It is the fifth element in Group 2, a soft silvery metallic alkaline earth metal. Because of its high chemical reactivity barium is never found in nature as a free element.

Physical properties

Phase at STPSolid
Density3.51 g/cm3
Atomic weight137.328 u

Thermal properties

Melting point1000 K
726.85 °C
1340.33 °F
Boiling point2118 K
1844.85 °C
3352.73 °F
Heat of vaporization140.2 kJ/mol

Atomic properties

Electronegativity (Pauling Scale)0.89
Electron affinity13.954 kJ/mol
Oxidation states+1, +2
(a strongly basic oxide)
Ionization energies
  1. 502.9 kJ/mol
  2. 965.2 kJ/mol
  3. 3600 kJ/mol

Electron configuration for barium

Electron configuration
Shorthand configuration
[Xe] 6s2
Electron configuration
Full configuration
1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 6s2
Electron configuration chart
Electrons per shell2, 8, 18, 18, 8, 2
Valence electrons 2
Valency electrons 2
Bohr model
BariumElectron shell for Barium, created by Injosoft ABBa
Figure: Shell diagram of Barium (Ba) atom.
Orbital Diagram

The history of Barium

DiscoveryCarl Wilhelm Scheele (1772)
First isolationHumphry Davy (1808)
Discovery of barium
Alchemists in the early Middle Ages knew about some barium minerals. Smooth pebble-like stones of mineral baryte were found in volcanic rock near Bologna, Italy, and so were called "Bologna stones". Alchemists were attracted to them because after exposure to light they would glow for years. The phosphorescent properties of baryte heated with organics were described by V. Casciorolus in 1602. Carl Scheele determined that baryte contained a new element in 1774, but could not isolate barium, only barium oxide. Johan Gottlieb Gahn also isolated barium oxide two years later in similar studies. Oxidized barium was at first called "barote" by Guyton de Morveau, a name that was changed by Antoine Lavoisier to baryta. Barium was first isolated by electrolysis of molten barium salts in 1808 by Sir Humphry Davy in England. Davy, by analogy with calcium, named "barium" after baryta, with the "-ium" ending signifying a metallic element.


List of unique identifiers for Barium in various chemical registry databases
CAS Number7440-39-3
ChemSpider ID4511436
EC number231-149-1
PubChem CID Number5355457