Oxygen
, Oxygen, symbol O, colorless, odorless, tasteless, slightly magnetic gaseous element. On earth, oxygen is more abundant than any other element. Oxygen was discovered in 1774 by the British chemist Joseph Priestley and, independently, by the Swedish chemist Carl Wilhelm Scheele ; it was shown to be an elemental gas by the French chemist Antoine Laurent Lavoisier in his classic experiments on combustion. PROPERTIES AND OCCURRENCE Gaseous oxygen can be condensed to a pale blue liquid that is strongly magnetic. Pale blue solid oxygen is produced by compressing the liquid. The atomic weight of oxygen is 15.9994; at atmospheric pressure, the element boils at -182.96° C (-297.33° F), melts at -218.4° C (-361.1° F), and has a density of 1.429 g/liter at 0° C (32° F). Oxygen composes 21 percent by volume or 23.15 percent by weight of the atmosphere; 85.8 percent by weight of the oceans (88.8 percent of pure water is oxygen); and, as a constituent of most rocks and minerals, 46.7 percent by w