Oxygen forms compounds with the other entire element except for the lighter noble gases. It is found in many mineral ores, in the form of oxides (O2-), sulfates (SO42-), nitrates (NO3-), phosphates (PO43-), carbonates (CO32-), silica and quartz (SiO2) and the silicates, etc. In the atmosphere, it is found in its elemental form, which is a diatomic molecule, O2, consisting of two atoms of oxygen joined by a double bond. (Actually, the bonding in O2 is quite a bit more complicated than that, because the second pair of electrons in the "double bond" are not paired.) When cooled to a temperature of -183ºC, oxygen forms a pale blue liquid, which is attracted to the poles of a very strong magnet.