Magnesium is a Block S, Group 2, Period 3 element. The electronic configuration is [Ne] 3s². In its elemental form magnesium's CAS number is 7439-95-4. The magnesium atom has a radius of 159.9.pm and it's Van der Waals radius is 173.pm. Magnesium the eighth most abundant element in the earth's crust. It is one third lighter than aluminum, and because of this is used in alloys that are essential for aerospace, satellite and missile construction. The metal improves the mechanical, fabrication, and welding characteristics of aluminum when used as an alloying agent. Uses also include flares and pyrotechnics due to its pyrophoric properties. Magnesium compounds, primarily magnesium oxide, are used mainly as refractory material in furnace linings for producing iron and steel, nonferrous metals, glass, and cement. High purity magnesium is found in dietary supplements.