Nitrogen belongs to the 15th group (according to the old classification, to the main subgroup of the 5th group), the 2nd period under 7 atomic number in the periodic system of chemical elements and is indicated by the symbol N. The molar mass of nitrogen is equal to 14 kg / mol.
Nitrogen, as a simple substance, is under normal conditions an inert diatomic gas that has no color, no taste, no smell. The atmosphere of the Earth is partially composed of this gas . The molecular mass of nitrogen is 28. The word "nitrogen" in Greek means "lifeless."
In nature, gas molecules consist of stable isotopes in which the molar mass of nitrogen is 14 kg / mol (99.635%) and 15 kg / mol (0.365%). Outside the Earth’s atmosphere, it is found in gas nebulae, in the atmosphere of the Sun, interstellar space, on the planets Neptune, Uranus and so on. It is the fourth in the solar system in terms of distribution after such elements as hydrogen, helium, oxygen. Radioactive isotopes are artificially obtained in which the molar mass of nitrogen is from 10 kg / mol to 13 kg / mol, and also from 16 kg / mol and up to 25 kg / mol. They all relate to short-lived elements. The most stable of the isotopes, in which the molar mass of nitrogen is 13 kg / mol, has a ten-minute half-life.
The biological role of this gas is huge, because it is one of the main elements that make up nucleic acids, proteins, nucleoproteins, chlorophyll, hemoglobin and other important substances. Both stable isotopes and a molar mass of nitrogen of 14 kg / mol and 15 kg / mol are involved in nitrogen exchange. For this reason, colossal amounts of bound nitrogen are contained in living organisms, “dead” organics and dispersed matter of oceans and seas. And in the future, as a result of decomposition and decay of organics containing nitrogen, deposits of nitrogen-containing organics such as, for example, nitrate, are formed.
About 160 species of microorganisms are able to bind and turn nitrogen from the atmosphere into digestible forms, for example, ammonium compounds, mainly consisting of a symbiotic relationship with higher plants, providing them with nitrogen fertilizers, and further along the food chain they reach herbivorous organisms and predators.
Under laboratory conditions, nitrogen is obtained by the decomposition reaction of ammonium nitrite. The result is a mixture of gas with ammonia, oxygen and nitric oxide (I). Its purification is carried out by passing the resulting mixture first through a solution of sulfuric acid, then iron (II) sulfate , and then over hot copper. Another way to get it in the laboratory is to pass ammonia over copper (II) oxide at a temperature of about 700 degrees Celsius.
On an industrial scale, nitrogen is obtained by passing air over hot coke, but not a pure product is formed, but again a mixture, but with noble gases and carbon dioxide, the so-called "air" or "generator" gas. It is a raw material for chemical synthesis and fuel. Nitrogen can also be emitted from the "generator" gas; for this, carbon monoxide is absorbed . The second method for producing nitrogen in industry is fractional distillation of liquid air.
There are also methods such as membrane and adsorption gas separation. It is possible to obtain atomic nitrogen, it is much more active than molecular nitrogen, capable of, for example, reacting under ordinary conditions with phosphorus, sulfur, arsenic, and metals. Nitrogen compounds are widely used in industry, they make fertilizers, explosives, medicines, dyes and so on. In the petrochemical industry, they purge pipelines, check their operation under pressure. In the mining complex, with its help, an explosion-proof environment is created inside the mines, rock layers are bursting with it. In electronics, they are blown over assemblies in which the slightest oxidation by oxygen in the air is unacceptable.