Period 3 element density and for its ability to resist corrosion due to the phenomenon of passivation. Structural components made from aluminium and its alloys are vital to the aerospace industry and are important in other areas of transportation and structural materials. The most useful compounds of aluminium, at least on a weight basis, are the oxides and sulfates. "Silicon" (symbol Si) is a tetravalent metalloid. It is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table. Controversy about silicon's character dates to
Molar volume Molar volume The molar volume, symbol "V", is the volume occupied by one mole of a substance (chemical element or chemical compound) at a given temperature and pressure. It is equal to the molar mass ("M") divided by the mass density (ρ). It has the SI unit cubic metres per mole (m/mol), although it is more practical to use the units cubic decimetres per mole (dm/mol) for gases and cubic centimetres per mole (cm/mol) for liquids and solids. The molar volume of a substance can be found by measuring its molar mass and density then applying the relation If the