(Gr. heios, the sun) First detected by Janssen in 1868. The second most abundant element in the universe. Found in the sun and other stars and involved in the production of energy from stars. The explosive energy from the hydrogen bomb is the fusion of hydrogen into helium. It expands upon cooling and is the only liquid which cannot be solidified by lowering the temperature to absolute zero at normal pressure.
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noble gas,unreactive,colorless,odorless,common isotopes are He-3 and He-4
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welding, as a protective gas for semiconductor materials,cooling in nuclear reactors, as a gas in supersonic wind tunnels,in a mixture of oxygen for work under pressure,filling balloons, pressurizing liquid fuel rockets.