tlenu

Tlenu is the Polish genitive singular form of the noun tlen, meaning oxygen. It is used in Polish to express possession or relation to oxygen, e.g., cząsteczka tlenu (an oxygen molecule).

Oxygen is a colorless, odorless gas at room temperature and the third most abundant element in the universe by mass. In pure form it is diatomic (O2) under normal conditions; ozone (O3) is a reactive allotrope that occurs in the Earth's stratosphere and protects against ultraviolet radiation.

On Earth, oxygen makes up about 21% of the atmosphere and is the most abundant element by mass in the Earth's crust (approximately 46%) and in water. It is essential for aerobic respiration in nearly all organisms and is transported in the blood via hemoglobin.

Industrial production is mainly by fractional distillation of liquefied air. Oxygen is used in metalworking, steel production, welding, chemical synthesis, medical oxygen therapy, and various combustion processes.

History: Oxygen was identified in the 1770s independently by Joseph Priestley and Carl Wilhelm Scheele. The name oxygen, proposed by Antoine Lavoisier, derives from Greek roots meaning “acid-former”; the initial hypothesis about acids being oxygen-containing was later revised.