Nitrogen is one of the most common elements of the Earth's atmosphere. It is a non-metallic chemical that has no color, taste or smell. Because of its abundance, it is also found in the structure of many compounds. Nitrogen is vital for life and most organisms need it. The air we breathe is mainly made up of nitrogen, we also consume a large amount every day as part of our food. This element has many industrial applications as well, being found in anesthetics such as nitrous oxide or super coolants like liquid nitrogen.

This element has the atomic number seven, which makes it the lightest in its group of chemical elements. In the periodic table of chemical elements, it was given the designation N. Bismuth, antimony and arsenic are part of the same chemical group, which means they share some common traits. The outermost electron shell of nitrogen has three missing electrons, which makes it very reactive, forming strong links with other elements. Due to the stability of these bonds, it can serve as a buffer gas.

Scientists estimate that nitrogen is the 7th most common element in the universe. Nitrogen is essential for life as a component in the structure of nucleic and amino acids, even if most organisms can't actually process pure nitrogen. It is essential to plants, being one of their main nutrients. Some plants, known as nitrogen fixers, are able to deposit the element in the soil and allow other species to use it.

Chemist and physician Daniel Rutherford discovered nitrogen in 1772, as part of his experiments on air. After eliminating carbon dioxide and oxygen, he found that the remaining gas was not flammable and didn't support life. Carl Wilhelm Scheele and Joseph Priestly also conducted similar tests and considered nitrogen to be air without oxygen, or burnt air. Antoine Laurent de Lavoisier named this gas "azote", meaning "lifeless", as part of his own experiments in 1786. All of these early pioneers observed that nitrogen is the inert part of air, which is unable to support life.

Some nitrogen compounds, such as nitric acid, were known way before the official discovery of the gas in 1772. Scientists were quick to notice that nitrogen doesn't burn and can't be breathed on its own. Because it is not flammable, nitrogen is often used today in the packaging of foods and explosives, as an inert gas that conserves these products safely.

While we breathe a lot of nitrogen as part of the air, the pure gas is dangerous. It can replace oxygen from the air, acting as an asphyxiant element. Liquid nitrogen is especially risky to handle because at room temperature it can turn into gas and make the air un-breathable. This is why ventilation is essential when liquid nitrogen is used. Divers can also suffer from decompression sickness, which is a condition caused by this gas. After sudden depressurization, bubbles of nitrogen accumulate in the blood, which can have very dangerous consequences, including death.

Ammonia (NH3) is probably the most important compound that includes nitrogen. Nitrogen reacts with hydrogen as part of the so-called Haber-Bosch process, which produces the colorless gas ammonia. It has a very strong and unpleasant smell but it is quite useful in industry, especially as part of nitrogen fertilizers. This is the use for more than 80% of the ammonia produced today. However, it is also an ingredient in cleaning solutions, textiles, pesticides, plastics and dyes, as well as an effective refrigerant gas.

The stars produce nitrogen through a process named fusion and eventually a large amount reaches the Earth's atmosphere. Both in terms of weight and volume, nitrogen makes up most of the atmosphere. It is also widespread in the whole universe, being considered the seventh most common chemical element by mass. Nitrogen is an essential part of nucleic acids, proteins and other molecules that are critical for organic life. Animal waste also has a large amount of nitrogen, in the form of uric acid, urea or ammonia.

Nitrogen is a strange element; even if it's harmless in the atmosphere it can be dangerous in pure form. Pure nitrogen replaces oxygen molecules in the air, making human breathing impossible. Inhaling the pure gas quickly leads to asphyxiation, as well as a dangerous condition known as decompression sickness, which is common in divers. It is a potentially fatal problem that is caused by the presence of nitrogen bubbles in the blood stream, usually as a result of surfacing too fast.

In normal conditions, 78.1% of our atmosphere consists of nitrogen. However, it is a lot rarer in the crust, which contains the same amount as the one of rare metals like lithium, niobium or gallium. Some minerals that include nitrogen are known, especially saltpetre (also known as nitre or potassium nitrate) and sodium nitrate (alternative names sodanitre or Chilean saltpetre). In the 1920s, the industrial production methods of ammonia and nitric acid were discovered, making these minerals less important.

Organisms source their nitrogen from the air and release excess amounts back to it. Plants are the main consumers of nitrogen but they can't use it in pure form, it has to be transformed into ammonia or another compound. Lightning strikes are one of the natural nitrogen fixation methods, the result being nitrogen oxides. However, the main source of fixation is diazotrophic bacteria, which use a process known as nitrogenases through the use of enzymes. Modern industrial plants also fixate a lot of air nitrogen into ammonia. Plants use nitrogen compounds such as ammonia to produce proteins. Animals eat the plants, transform plant proteins into proteins of their own and eliminate the extra amounts as waste.

When a plant or animal dies, it is oxidized and decomposed by environmental factors and bacteria. The nitrogen in its structure becomes free and returns to the atmosphere. Modern industrial techniques use the Haber process to fixate nitrogen, usually for the production of fertilizers. However, nitrogen-rich waste can be very dangerous for the environment. It destroys fresh and seawater and creates dead zones, as the bacteria that feed on nitrogen use all available water oxygen and the other species die. The process of denitrification generates nitrous oxide, which destroys the ozone layer.

Saltwater commercial fish farms use large quantities of trimethylamine oxide as a protection against osmosis. This chemical further converts into dimethylamine, which gives saltwater fish an unpleasant smell after a while and can help you detect the ones that are not fresh.

Nitric oxide is a free radical used by animals as a molecule that regulates blood circulation. This chemical immediately reacts with water, producing a chemical known as nitrite. Animals process the nitrogen found in plant proteins but don't use all of it and eliminate the rest as urea. Nitrogen is also found in nucleic acids and the excess is transformed into urea and uric acid. Rotten animal flesh has a distinct odour of decay, caused by the production of some amines with long chains, rich in nitrogen. Amino acids ornithine and lysine break down into a number of smelly compounds, in particular putrescine and cadaverine.