Oxygen

Oxygen is a chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group on the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as well as with other compounds. By mass, oxygen is the third-most abundant element in the universe, after hydrogen and helium. At standard temperature and pressure, two atoms of the element bind to form dioxygen, a colorless and odorless diatomic gas with the formula O2. Diatomic oxygen gas constitutes 20.8% of the Earth's atmosphere. As compounds including oxides, the element makes up almost half of the Earth's crust.

Discovery and naming

Phlogiston, a hypothetical substance, was used to explain combustion processes until the late 18th century. Carl Wilhelm Scheele, a Swedish chemist, and Joseph Priestley, an English chemist, independently discovered oxygen, but Priestley is usually given priority because his work was published first. The name oxygen was coined in 1777 by Antoine Lavoisier, whose experiments with oxygen helped to discredit the phlogiston theory of combustion and corrosion.

Characteristics

Oxygen is a highly reactive substance and must be segregated from combustible materials. The Earth's ozone layer is a high concentration of O3, or ozone, which is a molecule consisting of three oxygen atoms. Ozone is formed from dioxygen by the action of ultraviolet light and electrical discharges within the Earth's atmosphere.

Biological role

Oxygen is essential for cellular respiration in all aerobic organisms. Oxygen is used in mitochondria to help generate adenosine triphosphate (ATP) during oxidative phosphorylation. Reactive oxygen species, such as superoxide ion and hydrogen peroxide, are produced in cells and are used in certain cell signaling processes.

Industrial production

Oxygen is produced industrially by fractional distillation of liquefied air, use of zeolites with pressure swing adsorption to concentrate oxygen from air, electrolysis of water and other methods.

Safety

Oxygen presents both health and safety hazards. It is a strong oxidizer and presents a fire hazard. In the presence of a flame or spark, it can react with many common materials.

See also

• Oxygen therapy
• Oxygen cycle
• Oxygen evolution
• Oxygen sensor
• Oxygen concentrator

Oxygen Resources
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