Science / Periodic Table of Elements / Strontium (Sr): Atomic number: 38, Atomic mass: 87.62 g.mol -1, Electronegativity: 1.0, Density: 2.6 g.cm-3 at 20°C, Melting point: 769 °C, Boiling point: 1384 °C, Vanderwaals radius: 0.215 nm, Ionic radius: 0.113 nm (+2), Isotopes: 14, Electronic shell: [ Kr ] 5s2, Energy of first ionisation: 549.2 kJ.mol -1, Energy of second ionisation: 1064 kJ.mol -1, Discovered by: A. Crawford in 1790. Strontium is a soft, silver-yellow, alkaline-earth metal. It has three allotropic crystalline forms and in its physical and chemical properties it is similar to calcium and barium. Strontium reacts vigorously with water and quickly tarnishes in air, so it must be stored out of contact with air and water. Due to its extreme reactivity to air, this element always naturally occurs combined with other elements and compounds. Finely powdered strontium metal will ignite spontaneously in air to produce both strontium oxide and strontium nitride. Applications: Strontium has uses similar to those of calcium and barium, but it is rarely employed because of its higher cost. Principal uses of strontium compounds are in pyrotechnics, for the brilliant reds in fireworks and warning flares and in greases. A little is used as a getter in vacuum tubes to remove the last traces of air. Most strontium is used as the carbonate in special glass for television screens and visual display units. Although strontium-90 is a dangerously radioactive isotope, it is a useful by-product of nuclear reactors from whose spent fuel is extracted. Its high-energy radiation can be used to generate an electric current, and for this reason it can be used in space vehicles, remote weather stations and navigation buoys. Strontium in the environment: Strontium is commonly occurs in nature, formung about 0.034% of all igneous rock and in the form of the sulfate mineral celestite (SrSO4) and the carbonate strontianite (SrCO3). Celestite occurs frequently in sedimentary deposits of sufficient size, thus the development of mining facilities attractive. The main mining areas are UK, Mexico, Turkey and Spain. World production of strontium ores is about 140.000 tonnes per year from an unassessed total of reserves. Foods containing strontium range from very low e.g. in corn (0.4 ppm and oranged (0.5 ppm) to high, e.g. in cabbage (45 ppm), onions (50 ppm) and lattuce (74 ppm).
Science / Periodic Table of Elements / Strontium (Sr): Atomic number: 38, Atomic mass: 87.62 g.mol -1, Electronegativity: 1.0, Density: 2.6 g.cm-3 at 20°C, Melting point: 769 °C, Boiling point: 1384 °C, Vanderwaals radius: 0.215 nm, Ionic radius: 0.113 MORE