oxygens

Oxygen is the chemical element with the symbol O and atomic number 8. It is a colorless, odorless gas at room temperature and makes up about 21 percent of Earth’s atmosphere. In the solid and liquid states it readily combines with many elements to form oxides, and its high reactivity drives a wide range of natural and industrial processes.

The most important allotropes are diatomic oxygen (O2) and ozone (O3). O2 is essential for aerobic respiration in most living organisms and for most combustion processes. Ozone forms a layer in the stratosphere that absorbs ultraviolet radiation, helping to protect living organisms from DNA-damaging UV light. At ground level, ozone is a reactive oxidant that can impair respiratory health and contribute to smog.

Oxygen also exists in reactive forms such as singlet oxygen, which is an excited state used in certain chemical reactions and some biological processes. Its stable isotopes, 16O, 17O, and 18O, are used in geochemical and paleoclimate studies to trace ecological and atmospheric processes.

Oxygen is obtained industrially mainly by separating it from air, through methods such as fractional distillation of liquefied air or pressure swing adsorption. It is widely used in steelmaking and metal fabrication, chemical synthesis, welding and cutting, medical oxygen therapy, and in various laboratory and spaceflight applications. Biologically, it cycles through the environment via photosynthesis, respiration, and decomposition, linking atmospheric, aquatic, and terrestrial ecosystems.

Safety considerations include the fact that high oxygen concentrations support combustion and can pose fire hazards. Ozone at ground level is a pollutant and irritant, while excessive oxygen exposure can cause oxygen toxicity in certain settings.