Symbol	Ba
Atomnummer	56
Gruppe	2 (Jordalkalimetaller)
Periode	6
Blok	s
Klassifikation	Jordalkalimetal

Udseende	-
Farve	Sølv

Antal protoner	56 p+
Antal neutroner	81 n0
Antal elektroner	56 e-

Fra Wikipedia, den gratis encyklopædiBarium (af græsk; "barys", der betyder "tung") er det 56. grundstof i det periodiske system: Det har det kemiske symbol Ba, og under normale temperatur- og trykforhold optræder stoffet som et blødt, sølvhvidt metal med kemiske egenskaber, der minder om kalcium, blot mere reaktionsvilligt. Barium iltes ("ruster") meget let ved kontakt med atmosfærisk luft, og ved forbrænding i luft eller ilt danner det ikke blot bariumoxid (BaO), men også bariumperoxid (BaO₂). Barium reagerer med både vand og alkoholer under dannelse af gasformig brint samt bariumhydroxid; Ba(OH)₂. På grund af denne reaktionsvillighed må barium nødvendigvis opbevares i et vakuum eller i en væske, der ikke indeholder ilt, for at hindre luften i at få adgang til metallet.

Fase ved STP	Fast
Massefylde	3.51 g/cm3
Atommasse	137.328 u

Smeltepunkt	1000 K 726.85 °C 1340.33 °F
Kogepunkt	2118 K 1844.85 °C 3352.73 °F
Fordampningsvarme	140.2 kJ/mol

Elektronegativitet (Pauling Scale)	0.89
Elektronaffinitet	13.954 kJ/mol
Oxidationstrin	+1, +2 (a strongly basic oxide)
Ioniseringsenergier	502.9 kJ/mol 965.2 kJ/mol 3600 kJ/mol

Elektronkonfiguration Kortfattet konfiguration	[Xe] 6s2
Elektronkonfiguration Fuld konfiguration	1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 6s2
Elektronkonfigurationsdiagram	1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 6s2
Elektroner pr. Skal	2, 8, 18, 18, 8, 2
Valenselektroner	2
Valency-elektroner	2
Bohrs atommodel	Figur: Skaldiagram af Barium (Ba) atom.
Orbital diagram	1s 2s 2p 3s 3p 3d 4s 4p 4d 5s 5p 6s

Opdaget	Carl Wilhelm Scheele (1772)
Første isolation	Humphry Davy (1808)
Opdagelse af 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.

CAS Number	7440-39-3
ChemSpider ID	4511436
EC number	231-149-1
PubChem CID Number	5355457