DOE/LANL Jurisdiction Fire Danger Rating:

Barium

137.3

Barium

Element Stats

Select a temperature unit to update boiling and melting point values.

Physical

Physical Properties
Property	Value	Property	Value
Appearance	Soft, silvery-white metal that rapidly tarnishes in air
Classification	Alkaline Earth Metals	Density	3.594 g/cm³ at STP
Boiling Point	2118 K	Melting Point	1000 K

Atomic

Atomic Properties
Property	Value	Property	Value
Atomic Number	56	Atomic Mass	137.3277
Van Der Waals Radius	268	Atomic Radius (empirical)	222

Electronic & Chemical

Electronic and Chemical Properties
Property	Value	Property	Value
Electronegativity	0.89	Electron Affinity	13.954 kJ/mol
Electron Configuration	1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s²
Oxidation States	+2, +1
Ionization Energies	Showing all 3 ionization energies. 502.9 kJ/mol 965.2 kJ/mol 3600 kJ/mol

History

“Bologna stones” or lapis solaris—smooth pebbles of the barium-containing mineral baryte—can be found in volcanic rock near Bologna, Italy. Alchemists in the Middle Ages were fascinated by the baryte’s natural phosphorescence: when exposed to light, it would glow for years!

But it wasn’t until 1772 that Carl Scheele, a Swedish chemist, determined that baryte contained a new element. He was able to isolate barium oxide, but not barium itself. Barium is very reactive and is always bound to something when found in nature. Barium was first isolated by British chemist Sir Humprey Davy in 1808. Davy succeeded because he used the new process of electrolysis—using an electric current to drive the chemical separation. This method is still used to isolate barium today.

Properties

Barium is a soft metallic element and, when pure, is silvery white. It is also moderately heavy; in fact, it comes from the Greek word barys, which means heavy.

Barium loses electrons, or oxidizes, very easily. To keep it from oxidizing, it must be kept within oxygen-free liquids, such as petroleum.

Uses

Barium metal is present in many alloys, such as the barium-nickel alloy commonly used in automobile spark plugs. Barium compounds have many uses, too. Barium sulfate is a high-quality, permanent, white pigment that is used in paint, paper, and glassmaking. It is also used in medical imaging to boost contrast in x-ray diagnostics. “Barium meals” and “barium enemas” help visualize your digestive tract, often in real-time!

While barium sulfate is used safely in the medical field, other barium compounds have a dark side, like barium carbonate that is used as rat poison. But on the light side, barium nitrate is used to create yellow and apple-green colors in fireworks!

Compounds

The most important compounds are barium peroxide, chloride, sulfate, carbonate, nitrate, and chlorate.

All barium compounds that are soluble in water or acid are poisonous.

Forms

Naturally occurring barium is a mixture of seven isotopes. However, in all, barium has a whopping 40 known isotopes (only cesium, xenon, and mercury have about as many). The others are artificial (human-made) and usually unstable (radioactive). The naturally occurring isotopes are all stable except for one, barium-130, which is almost stable because it has a half-life of a billion trillion years! That’s about a hundred billion times longer than the current age of the universe. So even though barium-130 is radioactive, naturally occurring barium (which contains barium-130) is generally quite harmless.

Sources

Barium is found only in combination with other elements, usually barium sulfate (baryte). It is separated from the sulfate by electrolysis—using electricity to separate the elements.

Though not a major source—in fact, a very rare one—barium can also be found in a blue, fluorescent, precious gemstone called benitoite. It is the state gem of California.

Fun Facts

Baby, you're a firework!

Green fireworks are made with barium nitrate. Heat from the ignition of the firework causes a chemical reaction in the barium compounds, and they emit photons that fall within the range of green wavelengths.

He ain't heavy, he's my barium

Medical imaging often uses barium to help visualize what's going on in the body. Heavier elements, like barium, absorb and scatter x-rays really well, giving better images.

Spy vs Spy

In espionage, a barium pill isn’t an actual pill, but a secret way to track who is leaking information! A document might have a tiny, hard-to-spot difference, like a comma in one version and a semicolon in another. If the document gets leaked, you can check for that little detail to figure out who passed it on—pretty sneaky, right?

DOE/LANL Jurisdiction Fire Danger Rating:

Barium

137.3

Barium

Element Stats

Select a temperature unit to update boiling and melting point values.

Physical

Physical Properties
Property	Value	Property	Value
Appearance	Soft, silvery-white metal that rapidly tarnishes in air
Classification	Alkaline Earth Metals	Density	3.594 g/cm³ at STP
Boiling Point	2118 K	Melting Point	1000 K

Atomic

Atomic Properties
Property	Value	Property	Value
Atomic Number	56	Atomic Mass	137.3277
Van Der Waals Radius	268	Atomic Radius (empirical)	222

Electronic & Chemical

Electronic and Chemical Properties
Property	Value	Property	Value
Electronegativity	0.89	Electron Affinity	13.954 kJ/mol
Electron Configuration	1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s²
Oxidation States	+2, +1
Ionization Energies	Showing all 3 ionization energies. 502.9 kJ/mol 965.2 kJ/mol 3600 kJ/mol

History

Properties

Barium is a soft metallic element and, when pure, is silvery white. It is also moderately heavy; in fact, it comes from the Greek word barys, which means heavy.

Barium loses electrons, or oxidizes, very easily. To keep it from oxidizing, it must be kept within oxygen-free liquids, such as petroleum.

Uses

Compounds

The most important compounds are barium peroxide, chloride, sulfate, carbonate, nitrate, and chlorate.

All barium compounds that are soluble in water or acid are poisonous.

Forms

Sources

Barium is found only in combination with other elements, usually barium sulfate (baryte). It is separated from the sulfate by electrolysis—using electricity to separate the elements.

Though not a major source—in fact, a very rare one—barium can also be found in a blue, fluorescent, precious gemstone called benitoite. It is the state gem of California.

Fun Facts

Baby, you're a firework!

He ain't heavy, he's my barium

Medical imaging often uses barium to help visualize what's going on in the body. Heavier elements, like barium, absorb and scatter x-rays really well, giving better images.