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.

In its natural state, oxygen is a gas that makes up about 21% of Earth’s atmosphere. It is also the third most abundant element in the universe, after hydrogen and helium. Oxygen is essential for life as it is a critical component of the air we breathe and is required for the respiration process that occurs within cells to produce energy.

Oxygen is used in many industrial and medical applications, such as in the production of steel, in welding, and in the treatment of certain medical conditions such as respiratory distress. Oxygen is also used in rocket engines and is necessary for combustion to occur, which is why it is used as a key component of the fuel on rockets and spacecraft.

Oxygen is a highly reactive element and readily combines with other elements to form oxides. It is also capable of forming compounds with almost all other elements, including nitrogen, carbon, and hydrogen. Oxygens are critical element in the Earth’s biogeochemical cycles, as it is involved in the cycling of carbon, nitrogen, and other elements essential for life.