Barium (Ba)

Barium is the fifth chemical element in the periodic table of elements with the atomic number 56. Being a member of the alkaline earth metals family, this soft metal is divalent, electropositive, and reactive, and supports the formation of many compounds with other chemical elements, especially carbon, oxygen, and sulphur. Due to its high reactivity, barium cannot be found in the Earth’s crust in its elemental form. It mainly appears as a part of compounds.

Chemical and Physical Properties of Barium

The symbol in the periodic table of elementsBa
Atomic number56
Atomic weight (mass)137.33 g.mol-1
Group number2 (II a)
ColorSilvery-white metal
Physical stateSoft alkaline earth metal at room temperature
Electronegativity according to Pauling0.9 (χ = 0.89)
Density3.5 at 20°C
Melting point725 °C
Boiling point1640 °C
Van der Waals radius0.222 nm
Ionic radius0.135
Isotopes16 (6 stable isotopes)
Most characteristic isotope130-138Ba
Electronic shell[ Xe ] 6s2
The energy of the first ionization502.7 kJ.mol-1
The energy of the second ionization965 kJ.mol-1
Discovery dateIn 1808 by Sir Humphry Davy

In the periodic table, this dense and reactive chemical element is labeled with the symbol (Ba) and exhibits an oxidation state of +2. With the atomic number 56, atomic mass of 137.33 g.mol -1, and electronic configuration [ Xe ] 6s2, barium is a soft and easily breakable metal with Mohs hardness of 1.25.

It reaches its boiling point at 1640 °C, while the melting point is achieved at 725 °C. When barium is exposed to heat, it gives away a pale yellow-green flame.

This member of the alkaline earth metals family is an excellent conductor of electricity with an electronegativity of 0.9 according to Pauling, whereas the atomic radius according to van der Waals is 0.222 nm.    

Even though barium shares a large percent of the chemical properties with magnesium, strontium, and calcium, it’s far more reactive than them. Barium’s reactivity with oxygen, halogens, acids, and many other non-metal elements is so high that it must be kept in petroleum or kerosene in order to prevent uncontrolled chemical reactions.                    

How Was Barium Discovered?

The story of barium begins in 1600, when Vincenzo Casciarolo (Bologna, 1571 – Bologna, 1624, an Italian alchemist and shoemaker) tried to convert a stone to gold. Little did he know that that ‘stone’ was actually a barium sulfate (BaSO4).

By trying to reduce this chemical compound of barium with coal, Casciarolo succeeded in producing barium sulphide with luminescent properties in his small and improvised lab near Bologna, Italy. Namely, he’d exposed those ‘stone pebbles’ to sunshine, and at night, they had started glowing in the dark. 

By this mishap, this amateur chemist from Italy made great strides toward discovering  both barium and luminescence. This was also the first finding in the world of chemistry reporting an example of phosphor. Since Casciarolo failed to discover the ‘philosopher’s stone’ in his attempt to make gold out of the pebbles of an impure barium sulphate, his experiment was labeled as the ‘Bologna stone’, which is synonymous with the curiosity of this Italian alchemist. 

Many years later, in 1774, barium was recognised as a new chemical element. The Swedish scientist Carl W. Scheele was performing research on magnesium oxide which led him to the new discovery of barium oxide. In 1784, the English naturalist William Withering discovered the witherite (barium carbonate, BaCO3) after multiple experiments conducted on the heavy ore of “terra ponderosa”, excavated in Cumberland, England.

He then proved that barite and the mineral do not have identical chemical formulas and represent two separate minerals. 

However, the development of electrolysis in 1808 as one of the main techniques in chemical experiments provided the necessary means for isolating barium in its pure form.

Following the scientific work of the Swedish chemist Jacob Berzelius and his experience with electrolysis, the English chemist Sir Humphry Davy recreated the experiment in London and managed to decompose barium sulfate by conducting electrolysis of molten baryta (BaO).

In this way, he isolated pure barium metal at the Royal Institution in London. In a similar way, Davy also successfully isolated strontium. 

How Did Barium Get Its Name?

When Scheele discovered the new element in 1774, he named it ‘terra ponderosa’, which in Latin means ‘heavy earth’. Later, the Greek word “βαρύς” (barys), meaning “heavy”, was adopted for barium in order to depict its high atomic mass and density.

Where Can You Find Barium?

With a concentration of approximately 0.05% in the Earth’s crust, barium counts as the 14th most abundant substance of the periodic system of elements. Most commonly, this soft metal can be found in underground ore deposits of the mineral barite (barium sulphate [BaSO₄]) and witherite (barium carbonate [BaCO₃]).

They are located in hydrothermal and mesothermal metal ore veins, as well as in the sedimentary rock layers and volcanic rocks (basalts). Barium can also be produced by electrolysis of barium chloride – BaCl2.

Concentrations of barium can also be found in fish, some types of nuts, and seaweed. The world’s major barium ore mines are located in: 

  • The United States (South Dakota, Illinois, Tennessee, Nevada, Colorado, California, Arizona, Iowa, Oklahoma); 
  • Villamassargia, Sardinia, Italy; 
  • Les Malines, Gard, France;
  • Jinkouhe, Ebian, Sichuan Province, China; 
  • Huarihuyn, Huanuco, Peru;
  • Frizington, Cumbria, England;
  • Southern parts of India; 
  • Sidi Lahcen mine, Nador, Morocco; 
  • Khenifra, Mibladen, Morocco;
  • Grand Forks, British Columbia, Canada;
  • The Chech Republic.

Barium in Everyday Life

Barium has numerous applications in real life. Pure barium sulphate is applied in medicine as a contrast agent for performing x-ray diagnostics. Prior to making the x-ray images, patients are given a radio contrasting ‘barium meal’ (also: ‘barium enema’, or ‘barium swallow’) in order to coat the intestines with this chemical substance for better inspection of the digestive tract. 

The petroleum industry also benefits from the use of barium. Barium can be integrated in the drilling mud, or more specifically, as an additive to the drilling fluids that add weight while extracting gas or oil from oil wells. Furthermore, it’s used for:

  • Making glass;
  • Fluorescent lamps;
  • In fireworks, adding a green color to their display;
  • Making of tiles; 
  • Production of rubber;
  • In the barium-nickel alloy used in the making of spark-plug electrodes; 
  • As an additive to paints and paper pigments, known as blanc fixe, i.e. ‘permanent white’;
  • As a chemical getter for removing gas traces of carbon dioxide, nitrogen, oxygen, water vapor, or hydrogen from television picture vacuum tubes;
  • As a modifying agent. 

How Dangerous Is Barium?

Since barium is never found in its elemental form, only the barium compounds can present a real health hazard. As a result of the refining and extraction of oil, as well as coal mining, barium can be found in air, soil, and natural waters. 

Due to its water-solubility property, barium is mostly ingested via contaminated water. Inhalation of vapors released from barium sulphate and barium carbonate, as well as the skin contact with any of the poisonous barium-containing substances, can be a toxic hazard. The affected individual typically experiences the following symptoms triggered by the toxicity of barium:

  • Constipation;
  • Lightheadedness;
  • Increased blood pressure;
  • Severe allergic reactions;
  • Difficulty in breathing;
  • Irregular heart-rate;
  • Gastro-intestinal problems;
  • Swelling of the brain or the kidneys.

The exposure to harmful levels of barium via contaminated water or air mostly occurs in the workplace. Hence, barium toxicity can be labeled as an occupational hazard. The barium sulfate solution (meal) that is administered to patients during the x-ray diagnostics is not toxic since it cannot be absorbed in the body due to its heaviness. Also, there is no evidence that barium can cause cancerous mutation of cells. 

Isotopes of Barium

Among the 50 known isotopes of barium that range from barium-114 to barium-153, the most stable one is the barium-133 isotope. Its half-life is 10.51 years. Most barium isotopes are used in scientific research conducted in the field of nuclear physics. 

There are also ten meta states of barium. Having a half-life of 39 hours, barium-133m1 is the most stable barium meta state. 

The following is a tabular representation of the barium isotopes:


[n 1]

ZNIsotopic mass (Da)

[n 2][n 3]



[n 4]



[n 5][n 6]

Spin and


[n 7][n 8]

Natural abundance (mole fraction)
Excitation energyNormal proportionRange of variation
114Ba5658113.95068(15)530(230) ms

[0.43(+30−15) s]

β+, p (99.59%)113Xe0+  
α (.37%)110Xe
β+ (.04%)114Cs
CD (<.0034%)[n 9]102Sn, 12C
115Ba5659114.94737(64)#0.45(5) sβ+115Cs(5/2+)#  
β+, p114Xe
116Ba5660115.94138(43)#1.3(2) sβ+116Cs0+  
β+, p115Xe
117Ba5661116.93850(32)#1.75(7) sβ+117Cs(3/2)(+#)  
β+, α113I
β+, p116Xe
118Ba5662117.93304(21)#5.2(2) sβ+118Cs0+  
β+, p117Xe
119Ba5663118.93066(21)5.4(3) sβ+119Cs(5/2+)  
β+, p118Xe
120Ba5664119.92604(32)24(2) sβ+120Cs0+  
121Ba5665120.92405(15)29.7(15) sβ+ (99.98%)121Cs5/2(+)  
β+, p (.02%)120Xe
122Ba5666121.91990(3)1.95(15) minβ+122Cs0+  
123Ba5667122.918781(13)2.7(4) minβ+123Cs5/2(+)  
124Ba5668123.915094(13)11.0(5) minβ+124Cs0+  
125Ba5669124.914473(12)3.5(4) minβ+125Cs1/2(+#)  
126Ba5670125.911250(13)100(2) minβ+126Cs0+  
127Ba5671126.911094(12)12.7(4) minβ+127Cs1/2+  
127mBa80.33(12) keV1.9(2) sIT127Ba7/2−  
128Ba5672127.908318(11)2.43(5) dβ+128Cs0+  
129Ba5673128.908679(12)2.23(11) hβ+129Cs1/2+  
129mBa8.42(6) keV2.16(2) hβ+129Cs7/2+#  
130Ba[n 10]5674129.9063208(30)1.6(±1.1)×1021 yDouble EC130Xe0+0.00106(1) 
130mBa2475.12(18) keV9.54(14)msIT130Ba8−  
131Ba5675130.906941(3)11.50(6) dβ+131Cs1/2+  
131mBa187.14(12) keV14.6(2) minIT131Ba9/2−  
132Ba5676131.9050613(11)Observationally Stable[n 11]0+0.00101(1) 
133Ba5677132.9060075(11)10.51(5) yEC133Cs1/2+  
133mBa288.247(9) keV38.9(1) hIT (99.99%)133Ba11/2−  
EC (.0096%)133Cs
135mBa268.22(2) keV28.7(2) hIT135Ba11/2−  
136mBa2030.466(18) keV308.4(19) msIT136Ba7−  
137m1Ba661.659(3) keV2.552(1) minIT137Ba11/2−  
137m2Ba2349.1(4) keV0.59(10) µs  (17/2−)  
138Ba[n 12]5682137.9052472(5)Stable0+0.71698(42) 
138mBa2090.54(6) keV800(100) ns  6+  
139Ba[n 12]5683138.9088413(5)83.06(28) minβ139La7/2−  
140Ba[n 12]5684139.910605(9)12.752(3) dβ140La0+  
141Ba[n 12]5685140.914411(9)18.27(7) minβ141La3/2−  
142Ba[n 12]5686141.916453(7)10.6(2) minβ142La0+  
143Ba[n 12]5687142.920627(14)14.5(3) sβ143La5/2−  
144Ba[n 12]5688143.922953(14)11.5(2) sβ144La0+  
145Ba5689144.92763(8)4.31(16) sβ145La5/2−  
146Ba5690145.93022(8)2.22(7) sβ (99.98%)146La0+  
β, n (.02%)145La
147Ba5691146.93495(22)#0.893(1) sβ (99.94%)147La(3/2+)  
β, n (.06%)146La
148Ba5692147.93772(9)0.612(17) sβ (99.6%)148La0+  
β, n (.4%)147La
149Ba5693148.94258(21)#344(7) msβ (99.57%)149La3/2−#  
β, n (.43%)148La
150Ba5694149.94568(43)#300 msβ150La0+  
β, n (rare)149La
151Ba5695150.95081(43)#200# ms [>300 ns]β151La3/2−#  
152Ba5696151.95427(54)#100# msβ152La0+  
153Ba5697152.95961(86)#80# msβ153La5/2−#  

Source: Wikipedia

List of Barium Compounds 

Barium is a highly reactive divalent chemical element that forms hydrides, fluorides, chlorides, bromides, iodides, oxides, sulphides, selenides, and nitrides. The most significant barium compounds are barium sulfate (barite), occurring in a crystal form, and barium carbonate (witherite), occurring in a mineral form.

The list of barium compounds formed by reacting with other chemical elements is as follows:

  • Barium acetate;
  • Barium acetylacetonate;
  • Barium azide;
  • Barium borate;
  • Barium boride;
  • Barium bromide;
  • Barium carbide;
  • Barium carbonate;
  • Barium chlorate;
  • Barium chloride;
  • Barium chromate;
  • Barium cyanide;
  • Barium ferrate;
  • Barium ferrite;
  • Barium fluoride;
  • Barium hydride;
  • Barium hydroxide;
  • Barium hypochlorite;
  • Barium iodate;
  • Barium iodide;
  • Barium manganate;
  • Barium metaphosphate;
  • Barium nitrate;
  • Barium orthotitanate;
  • Barium oxalate;
  • Barium oxide;
  • Barium perchlorate;
  • Barium permanganate;
  • Barium peroxide;
  • Barium stannate;
  • Barium sulfate;
  • Barium sulfide;
  • Barium sulfite;
  • Barium titanate;
  • Barium tungstate;
  • BaZnGa;
  • Europium barium titanate;
  • Han purple and Han blue;
  • Lanthanum barium copper oxide;
  • Lithopone;
  • Rare-earth barium copper oxide;
  • Strontium barium niobate;
  • Thallium barium calcium copper oxide;
  • Yttrium barium copper oxide.


Barite is a mineral of barium sulphate [BaSO₄] and it’s the main source of barium in nature. It appears as white to colorless, yellow, pink, red, purple, orange, blue, green, or black prismatic crystal formations.

The barite crystals can appear as fluorescent or even phosphorescent and in a vast variety of shapes: bladed, nodular, stalactitic, or fibrous. Barium sulphate deposits often occur in beautiful formations resembling a rosette. 

These minerals are commonly associated with: 

  • Aragonite; 
  • Anglesite;
  • Apatite;
  • Calcite;
  • Celestine; 
  • Chalcopyrite;
  • Dolomite;
  • Fluorite;
  • Feldspars;
  • Gypsum; 
  • Quartz; 
  • Sulfur.


The mineral witherite (barium carbonate [BaCO₃]) was named by Abraham Gottlob Werner in honor of its founder, the English geologist, botanist, and naturalist, William Withering (1741-1799). It occurs in galena ores (an octahedral sulfide group of minerals) in various colors, mostly white, grayish-white, creamy-white, pale yellow, or pale green. The bladed or tabular crystals of whiterite very often occur in an intertwined form of massive crystal clusters.

Witherite is found in the following locations in the United States:

  • El Portal, Mariposa Co., California;
  • Minerva No. 1 Mine, Cave-in-Rock, Hardin Co., Illinois;
  • the Pigeon Roost Mine, Glenwood, Montgomery Co., Arkansas.

5 Interesting Facts And Explanations

  1. The alkaline earth metals group of the periodic system of elements consists of the following chemical substances: magnesium (Mg), strontium (Sr), radium (Ra), beryllium (Be), calcium (Ca), and barium (Ba)
  2. The alkaline earth metals that form the Group 2 (II a) on the periodic table are so soft that they can be cut with a simple sharp object. 
  3. The property of a substance to produce light when it’s not exposed to a heating source is called luminescence. 
  4. Benitoite is a barium mineral that occurs in a form of a blue fluorescent gemstone. Being very rare, it’s made California’s official gemstone.
  5. The volatile barium compounds produce green-hued flames. This property is used as one of the parameters in the quality assessment of barite.