A measure of how difficult it is to deform a material. It is given by the ratio of the shear stress to the shear strain. A measure of how difficult it is to compress a substance. It is given by the ratio of the pressure on a body to the fractional decrease in volume. A measure of the propensity of a substance to evaporate. It is defined as the equilibrium pressure exerted by the gas produced above a substance in a closed system.
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Nor shall the RSC be in any event liable for any damage to your computer equipment or software which may occur on account of your access to or use of the Site, or your downloading of materials, data, text, software, or images from the Site, whether caused by a virus, bug or otherwise. Jump to main content. Periodic Table. Glossary Allotropes Some elements exist in several different structural forms, called allotropes.
Discovery date Discovered by Humphry Davy Origin of the name The name comes from the Greek 'barys', meaning heavy. Glossary Group A vertical column in the periodic table. Fact box. Glossary Image explanation Murray Robertson is the artist behind the images which make up Visual Elements. Appearance The description of the element in its natural form.
Biological role The role of the element in humans, animals and plants. Natural abundance Where the element is most commonly found in nature, and how it is sourced commercially. Uses and properties. Image explanation. Barium is a soft, silvery metal that rapidly tarnishes in air and reacts with water. Barium is not an extensively used element. Most is used in drilling fluids for oil and gas wells. It is also used in paint and in glassmaking. All barium compounds are toxic; however, barium sulfate is insoluble and so can be safely swallowed.
A suspension of barium sulfate is sometimes given to patients suffering from digestive disorders. Barium is a heavy element and scatters X-rays, so as it passes through the body the stomach and intestines can be distinguished on an X-ray.
Barium carbonate has been used in the past as a rat poison. Barium nitrate gives fireworks a green colour. Biological role. Barium has no known biological role, although barium sulfate has been found in one particular type of algae. Barium is toxic, as are its water- or acid-soluble compounds. Natural abundance. Barium occurs only in combination with other elements. The major ores are barite barium sulfate and witherite barium carbonate. Barium metal can be prepared by electrolysis of molten barium chloride, or by heating barium oxide with aluminium powder.
Help text not available for this section currently. Elements and Periodic Table History. In the early s, Vincenzo Casciarolo, of Bologna, Italy, found some unusual pebbles. If they were heated to redness during the day, they would shine during the night. This was the mineral barite barium sulfate, BaSO 4. When Bologna stone, as it became known, was investigated by Carl Scheele in s he realised it was the sulfate of an unknown element. Meanwhile a mineralogist, Dr William Withering, had found another curiously heavy mineral in a lead mine in Cumberland which clearly was not a lead ore.
He named it witherite; it was later shown to be barium carbonate, BaCO 3. Neither the sulfate nor the carbonate yielded up the metal itself using the conventional process of smelting with carbon. Barium nitrate Ba NO 3 2 burns with a bright green color and is used in signal flares and fireworks.
Barium chloride BaCl is used as a water softener. Barium oxide BaO easily absorbs moisture and is used as a desiccant. Barium peroxide BaO 2 forms hydrogen peroxide H 2 O 2 when it is mixed with water and is used as a bleaching agent that activates when wet.
Barium titanate BaTiO 3 is used as a dielectric material in capacitors. Bariumm, a radioactive form of barium produced by the decay of cesium , has a relatively short half-life and is commonly used in high school and college physics half-life determination experiments. Estimated Crustal Abundance : 4. Estimated Oceanic Abundance : 1. Vincenzo Casciarolo, a 17th-century Italian alchemist, first noticed barium in the form of unusual pebbles that glowed for years after exposure to heat, according to the Royal Society of Chemistry.
He named these pebbles "Bologna stones" after his hometown, but they were later determined to be barium sulfate BaSO 4. Pure barium metal was not isolated and identified until at the Royal Institution in London. The prominent chemist and inventor Sir Humphry Davy used electrolysis to separate the barium from molten barium salts such as barium hydroxide Ba OH 2. During electrolysis, an electric current is run through the ionic substance in order to separate ions from each other. Because the barium salts were molten, the barium ions easily moved to the container with the negative electrode, and the other negative ions easily moved in the opposite direction to the container with the positive electrode.
Barium is found naturally only in combination with other elements because of its high level of reactivity. Barium is most commonly found combined with sulfate and carbonate, but can also form compounds with hydroxide, chloride, nitrate, chlorate, and other negative ions.
About 0. In order to obtain pure elemental barium, it must be separated from other elements present in naturally occurring barium compounds. Barium oxidizes in air, reacts vigoroulsy with water to form the hydroxide, liberating hydrogen. Barium reacts with almost all the non-metals, forming often poisouning compounds. Barium is often used in barium-nickel alloys for spark-plug electrodes an in vacuum tubes as drying and oxygen-removing agent.
It is also used in fluorescent lamps: impure barium sulfide phosphoresces after exposure to the light. Barium compounds are used by the oil and gas industries to make drilling mud. Drilling mud simplifies drilling through rocks by lubricating the drill.
Barium compounds are also used to make paint, bricks, tiles, glass, and rubber. Barium nitrate and clorate give fireworks a green colour. Barium is surprisingly abundant in the Earth's crust, being the 14th most abundant element. High amounts of barium may only be found in soils and in food, such as nuts, seaweed, fish and certain plants.
Because of the extensive use of barium in the industries human activities add greatly to the release of barium in the environment. As a result barium concentrations in air, water and soil may be higher than naturally occurring concentrations on many locations.
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