Barium Facts – Element 56 or Symbol Ba

Barium Facts

Barium is a chemical element with the symbol Ba and atomic number 56. It is an alkaline earth metal that is best known for the green color it adds to fireworks and for its use in barium enemas for x-ray imaging.

Discovery, Naming, and Isolation

Pebbles consisting of the mineral baryte occurred in volcanic rock in Italy. Following exposure to light, these stones glowed with phosphorescence, making them extremely interesting to alchemists in the early 17th century.

In 1772, Carl Wilhelm Scheele experimented with baryte, believing its interesting properties meant it contained a new element. But, Scheele could only isolate barium oxide, not the purified element. In 1808, Sir Humphry Davy used electrolysis to isolate the element from barium hydroxide.

Davy named the “barium” from the Greek word “barys,” meaning “heavy,” due to the high density of its compounds. He added the -ium ending consistent with the names of other metallic elements.

Electron Levels of a Barium Atom

Appearance and Properties

Pure barium is a silvery-white metal with a slight golden cast that is soft enough to cut with a knife. It is highly reactive and rapidly oxidizes in air, forming a dark gray protective layer of barium oxide. Barium reacts with water, releasing hydrogen gas, and it reacts vigorously with halogens to form halides. Barium compounds burn with a green flame. Chemically, barium acts much like magnesium, calcium, and strontium.

Element Group

Barium is part of Group 2 on the periodic table, which is also known as the alkaline earth metals. These elements share similar properties, including high reactivity with water, a strong tendency to form oxides, and a common +2 oxidation state.

Natural and Synthetic Isotopes

Natural barium is a mix of seven isotopes: Ba-130, Ba-132, and Ba-134-138. Barium-138 is the most abundant, accounting for about 71.7% of all natural barium. Ba-130 and Ba-133 are radioisotopes. Ba-133 has a half-life of 10.51 years. Ba-130 is essentially stable, with a half-life of around 1021 years. Including the synthetic radioisotopes, there are 40 known barium isotopes with masses from 144 to 153.

Abundance and Sources

Barium is the 14th most abundant element in the Earth’s crust, accounting for 0.0425% of the crust and having a concentration of 13 μg/L in sea water. The element is too reactive to occur as a native element. It mainly occurs in the form of the minerals baryte (barite, barium sulfate) and witherite (barium carbonate).

The largest sources of barium are in Britain, Romania, and Russia. The main producers are China, India, Morocco, and the United States.


Barium purification relies on electrolysis or high-temperature reduction. Electrolysis involves dissolving barium compounds in molten salts, then using electric current to isolate the metal. High-temperature reduction uses aluminum or other metals to reduce barium compounds, ultimately leaving barium in its pure form.

Uses of Barium

Barium and its compounds have numerous applications, including:

  • Medical Imaging: Barium sulfate is a contrast agent in gastrointestinal X-rays and other imaging techniques due to its opacity to X-rays.
  • Oil and Gas Drilling: Barium sulfate is a key component in drilling fluids, providing weight and lubrication to prevent blowouts.
  • Gemstone: The blue fluorescent gemstone benitoite (barium titanate silicate) is the state gem of California.
  • Manufacturing: Barium is used in the production of glass, ceramics, and as a deoxidizing agent in metallurgical processes.
  • Fireworks and Pyrotechnics: Barium nitrate, barium monochloride, and barium chlorate produce green colors in fireworks.
  • Electronics: Barium titanate is a piezoelectric material used in capacitors and transducers. Historically, it was a getter in vacuum tubes for removing unwanted gases. Barium ferrite is a magnetic compound in magnetic stripe cards and data storage tapes.
  • Superconductors: YBCO is a well-known high-temperature superconductor containing barium.
  • Water Treatment: Barium carbonate is used to remove impurities, such as sulfates, from water.
  • Rodenticide: Water-soluble barium compounds are toxic and effective as rodenticides.
  • Poison: For the same reason, soluble compounds have been used in poisonings.
  • Oceanography: Barium concentration in sea water shows a correlation with silicic acid and alkalinity. Meanwhile, particulate barium correlates with particulate organic carbon. The element helps trace variations in the global climate and carbon cycle.

Oxidation States

Barium typically exhibits a +2 oxidation state, which is consistent with other alkaline earth metals. This state is the most stable and is the one observed in most of its compounds. However, it sometimes exhibits the +1 oxidation state.

Biological Role, Health Effects, and Toxicity

Barium has no known biological role in humans or other living organisms. The element is not a carcinogen and does not bioaccumulate. Insoluble compounds, like barium sulfate, present no significant health risk. However, soluble ones (e.g., barium chloride) cause severe health effects, including muscle weakness, respiratory distress, and cardiac irregularities. The Ba2+ ion blocks potassium ion channels, which leads to nervous system and organ damage. Inhaling insoluble barium compounds leads to a condition called baritosis, which is similar to coal miner’s lung and silicosis.

Key Barium Facts for Scientists

Here’s a table with key facts about barium, including its physical and atomic properties:

Atomic Number56
Atomic Weight137.327
Group2 (Alkaline Earth Metals)
Electron Configuration[Xe] 6s²
Electrons per Shell2, 8, 18, 18, 8, 2
State at Room TemperatureSolid
Melting Point727 °C (1341 °F)
Boiling Point1845 °C (3353 °F)
Density3.59 g/cm³
Heat of Fusion7.12 kJ/mol
Heat of Vaporization142 kJ/mol
Molar Heat Capacity28.07 J/(mol·K)
Oxidation States+1, +2
Electronegativity0.89 (Pauling scale)
First Ionization Energy502.9 kJ/mol
Second Ionization Energy965.2 kJ/mol
Third Ionization Energy3,613 kJ/mol
Atomic Radius222 pm
Covalent Radius215 pm
Van der Waals Radius268 pm
Crystal StructureBody-centered cubic (bcc)
Thermal Conductivity18.4 W/(m·K)
Electrical Resistivity332 nΩ·m
Magnetic OrderingParamagnetic
Young’s Modulus13 GPa
Shear Modulus4.9 GPa
Mohs Hardness1.25


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