Oxygen and its compounds play a key role in many of the important processes of life and industry. Oxygen in the biosphere is essential in the processes of respiration and metabolism, the means by which animals derive the energy needed to sustain life. Furthermore, oxygen is the most abundant element at the surface of the Earth. In combined form it is found in ores, earths, rocks, and gemstones, as well as in all living organisms. Oxygen is a gaseous chemical element in
Group VA of the periodic table. The chemical symbol for atomic oxygen is O, its atomic number is 8, and its atomic weight is 15.9994. Elemental oxygen is known principally in the gaseous form as the diatomic molecule, which makes up 20.95% of the volume of dry air. …show more content…
(atomic) percent oxygen in combination with silicon and one or more metallic elements. Several important ores are principally oxides of the desired metals, such as the important iron-bearing minerals hematite, magnetite, and limonite and the most important aluminum-bearing mineral, BAUXITE (a mixture of hydrated aluminum oxides and iron oxide).
PHYSICAL AND CHEMICAL PROPERTIES
Three naturally occurring isotopes of oxygen have been found: one with mass 16
(99. 759% of all oxygen), one with mass 17 (0.037%); and one with mass 18
(0.204%). The rarer isotopes, principally the latter, find their major use in labeling experiments used by scientists to follow the steps of chemical reactions. If oxygen at a pressure of one atmosphere is cooled, it will liquefy at 90.18 K (-182.97 deg C; -297.35 deg F), the normal boiling point of oxygen, and it will solidify at 54.39 K