nitrojeni

Nitrojeni, or nitrogen (symbol N, atomic number 7), is a nonmetal that exists as a diatomic gas at standard conditions and makes up about 78 percent of Earth's atmosphere.

In its elemental form it is N2, a diatomic molecule with a triple bond that makes it relatively unreactive. It is colorless, odorless, and tasteless.

Occurrence and biology: Most nitrogen is in the atmosphere as N2; biological availability requires fixation to ammonia or nitrate. It is an essential nutrient and cycles through fixation, assimilation, mineralization, nitrification, and denitrification. Stable isotopes are 14N and 15N; 13N is used in PET.

Production and use: Commercial nitrogen is obtained from air by fractional distillation of liquid air, cryogenic separation, or pressure swing adsorption. It underpins the Haber-Bosch process to synthesize ammonia: N2 + 3 H2 → 2 NH3.

Applications: fertilizers, inert atmospheres for welding and chemical processing, food packaging, electronics, and cryogenics.

Safety and environment: nitrogen is generally non-toxic but acts as an asphyxiant; displaces oxygen. Liquid nitrogen can cause cold burns. Nitrogen oxides formed during combustion contribute to air pollution; excessive fertilizer use can cause eutrophication.

History: Daniel Rutherford described the gas in 1772 as noxious air (azote); the name nitrogen was adopted in the 19th century.