Radium (Ra): Atomic number: 88, Atomic mass: 226.0254 g.mol -1, Electronegativity: 0.9, Density: 5 g.cm-3 at 20°C, Melting point: 700 °C, Boiling point: 1140 °C, Vanderwaals radius: 0.230 nm, Ionic radius: unknown, Isotopes: 6, Electronic shell: [ Rn ] 7s2, Energy of first ionisation: 509.1 kJ.mol -1, Energy of second ionisation: 975 kJ.mol -1, Discovered by: Pierre and Marie Curie 1898. Radium is silvery, lustrous, soft, intensely radioactive. It readily oxidizes on exposure to air, turning from almost pure white to black. Radium is luminescent, corrodes in water to form radium hydroxide. Although is the heaviest member of the alkaline-earth group it is the most volatile. Applications: Radium is used in luminous paint (in the form of radium bromide). Radium and beryllium were once used as a portable source of neutrons. Radium is used in medicine to produce radon gas, used for cancer treatment. At the beginning of the 19th century radium was used as additive in products like toothpaste, hair creams and even food items. Radium in the environment: It has been estimated that each square kilometer of the earth surface (to a depth of 40 cm) contains 1 gram of radium. Early in the twentieth century radium was extracted from uranium ores for use in luminous dials and medical treatment. The amount of radium in uranium ores varies between 150 and 350 mg/ton. The most in contained in the ores of Zaire and Canada.

 

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Radium (Ra): Atomic number: 88, Atomic mass: 226.0254 g.mol -1, Electronegativity: 0.9, Density: 5 g.cm-3 at 20°C, Melting point: 700 °C, Boiling point: 1140 °C, Vanderwaals radius: 0.230 nm, Ionic radiu . . . View Full Definition

Revenue Assurance (RA): A form of revenue insurance that protects a grower of an insurable crop whenever low prices, low yields, or a combination of both causes revenue to fall below a guaranteed level selected by . . . View Full Definition

Alkaline Earth Metal: The Group 2 elements, beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra) form alkaline oxides and hydroxides and are called 'alkaline earth metals'.