In 1929, W. F. Giaque and H. L. Johnston announced the discovery of two isotopes of oxygen, of mass numbers 17 and 18. It is denser than air and only slightly soluble in water. A poor conductor of heat and electricity, oxygen supports combustion but does not burn. Oxygen is paramagnetic in its solid, liquid, and gaseous forms. 2 Oxygen is extremely active chemically, forming compounds with almost all of the elements except the inert gases.
Oxygen unites directly with a number of other elements to form oxides .
It is a constituent of many acids and of hydroxides, carbohydrates, proteins, fats and oils, alcohols, cellulose, and numerous other compounds such as the carbonates, chlorates, nitrates and nitrites, phosphates and phosphites, and sulphates and sulphites. The burning of substances in air is rapid oxidation or combustion . The respiration of animals and plants is a form of oxidation essential to the liberation of the energy stored in such food materials as carbohydrates and fats. The rusting of iron and the corrosion of many metals results from the action of the oxygen in the air. 4 Natural Occurrence and Preparation Oxygen is the most abundant element on earth, constituting about half of the total material of its surface.