(măg-nēʹzē-əm, -zhəm) noun. Symbol MgA light, silvery-white, moderately hard metallic element that in ribbon or powder form burns with a brilliant white flame. It is used in structural alloys, pyrotechnics, flash photography, and incendiary bombs. Atomic number 12; atomic weight 24.312; melting point 649°C; boiling point 1,090°C; specific gravity 1.74 (at 20°C); valence 2, magnesium.
magnesium oxide (măg-nēʹzē-əm ŏkʹsĪd´) noun. A white, powdery compound, MgO, having a high melting point (2,800°C), used in high-temperature refractories, electrical insulation, food packaging, cosmetics, and pharmaceuticals, magnesium oksida.