Nitrogen
Nitrogen is a common element in the universe, estimated at about seventh in total abundance in our galaxy and the Solar System. It is synthesised by fusion of carbon and hydrogen in supernovas. Due to the volatility of elemental nitrogen and its common compounds with hydrogen and oxygen, nitrogen is far less common on the rocky planets of the inner Solar System, and it is a relatively rare element on Earth as a whole. However, as on Earth, nitrogen and its compounds occur commonly as gases in the atmospheres of planets and moons that have atmospheres.
Many industrially important compounds, such as ammonia, nitric acid, organic nitrates (propellants and explosives), and cyanides, contain nitrogen. The extremely strong bond in elemental nitrogen dominates nitrogen chemistry, causing difficulty for both organisms and industry in converting (or "fixing") the N2 into useful compounds, but at the same time causing release of large amounts of often useful energy when the compounds burn, explode, or decay back into nitrogen gas. Synthetically-produced ammonia and nitrates are key industrial fertilizers and fertilizer nitrates are key pollutants in causing the eutrophication of water systems.
Outside their major uses as fertilizers and energy-stores, nitrogen compounds are versitile organics. Nitrogen is part of materials as diverse as Kevlar fabric and cyanoacrylate "super" glue. Nitrogen is a constituent of molecules in every major pharmacological drug class, including the antibiotics. Many drugs are mimics or prodrugs of natural nitrogen-containing signal molecules: for example, the organic nitrates nitroglycerin and nitroprusside control blood pressure by being metabolized to natural nitric oxide. Plant alkaloids (often defense chemicals) contain nitrogen by definition, and thus many notable nitrogen-containing drugs, such as caffeine and morphine are either alkaloids or synthetic mimics that act (as many plant alkaloids do) upon receptors of animal neurotransmitters (for example, synthetic amphetamines).
Nitrogen occurs in all organisms, primarily in amino acids (and thus proteins) and also in the nucleic acids (DNA and RNA). The human body contains about 3% by weight of nitrogen, the fourth most abundant element in the body after oxygen, carbon, and hydrogen. The nitrogen cycle describes movement of the element from the air into the biosphere and organic compounds, then back into the atmosphere.
Occurrence
Nitrogen is the largest constituent of the Earth's atmosphere (78.082% by volume of dry air, 75.3% by weight in dry air). However, this high concentration does not reflect nitrogen's overall low abundance in the makeup of the Earth, from which most of the element escaped by solar evaporation, early in the planet's formation.
Nitrogen is a common element in the universe, and is estimated to be approximately seventh most abundant chemical element by mass in the universe, our galaxy and the Solar System. Its occurrence there is thought to be entirely due to synthesis by fusion from carbon and hydrogen in supernovas. In these places it was originally created by fusion processes from carbon and hydrogen in supernovas. Molecular nitrogen and nitrogen compounds have been detected in interstellar space by astronomers using the Far Ultraviolet Spectroscopic Explorer.
Due to the volatility of elemental nitrogen and also its common compounds with hydrogen and oxygen, nitrogen and its compounds were driven out of the planetesimals in the early Solar System by the heat of the Sun, and in the form of gases, were lost to the rocky planets of the inner Solar System. Nitrogen is therefore a relatively rare element on these inner planets, including Earth, as a whole. In this, nitrogen resembles neon, which has a similar abundance in the universe, but is also rare in the inner Solar System. Nitrogen is estimated at 30th of the elements in crustal abundance. There exist some relatively uncommon nitrogen minerals, such as saltpetre (potassium nitrate), Chile saltpetre (sodium nitrate) and sal ammoniac (ammonium chloride). Even these are known mainly as concentrated from evaporative ocean beds, due to their ready solubility of most naturally-occurring nitrogen compounds in water. A similar pattern occurs with the water solubility of the uncommon light element boron.
However, nitrogen and its compounds occur far more commonly as gases in the atmospheres of planets and moons that are large enough to have atmospheres.[a] For example, molecular nitrogen is a major constituent of not only Earth's atmosphere, but also the Saturnian moon Titan's thick atmosphere. Also, due to retension by gravity at colder temperatures, nitrogen and its compounds occur in appreciable to trace amounts in planetary atmospheres of the gas giant planets.
Nitrogen is present in all living organisms, in proteins, nucleic acids, and other molecules. It typically makes up around 4% of the dry weight of plant matter, and around 3% of the weight of the human body. It is a large component of animal waste (for example, guano), usually in the form of urea, uric acid, ammonium compounds, and derivatives of these nitrogenous products, which are essential nutrients for all plants that cannot fix atmospheric nitrogen.
| Symbol | N | |
| Atomic Number | 7 | |
| Atomic Weight | 14.00674 | |
| Oxidation States | +1,+2,+3,+4,+5,-1,-2,-3 | |
| Electronegativity, Pauling | 3.04 | |
| State at RT | Gas, Nonmetal | |
| Melting Point, K | 63.29 | |
| Boiling Point, K | 77.4 |
Interesting Facts about Nitrogen
- About 2.5 percent of the weight of living organisms comes from nitrogen in organic molecules.
- Many of the molecules of life contain nitrogen. It is the fourth most abundant element in the human body.
- The nitrogen compound nitroglycerin has two rather different uses: blowing things up, and relief of angina, a life threatening heart condition.
- Alfred Nobel funded the annual Nobel Prizes with the fortune he made from manufacturing dynamite, whose key ingredient is nitroglycerin. Ironically, in his later years he suffered from angina and took nitroglycerin to relieve the symptoms.
- Neptune’s satellite Triton has five mile high, nitrogen-powered geysers.
- Like Earth, Triton’s atmosphere is mainly nitrogen, but Triton is so cold the nitrogen sits on the surface as a rock-hard solid. The solid nitrogen allows the feeble light arriving from the sun to pass through it. Dark impurities in the nitrogen ice or in darker rocks below the ice warm up slightly in the sunlight, melting and vaporizing the solid nitrogen, which eventually breaks through the solid nitrogen as geysers which push ice particles one to five miles above Triton’s frozen surface.
- Nitrogen is the seventh most abundant element in the universe.
- In 1919, the world learned for the first time that atomic nuclei could be disintegrated. Ernest Rutherford reported that he had bombarded nitrogen gas with alpha-particles (helium nuclei) and found hydrogen was produced. (Further research by Patrick Blackett showed that the alpha particles had transmuted nitrogen-14 to oxygen-17 plus hydrogen.)
- The universe’s nitrogen was made, and is being made, by the CNO cycle in stars heavier than our sun.
Appearance and Characteristics
Harmful effects:
- Nitrogen is non-toxic under normal conditions.
- Direct skin contact with liquid nitrogen causes severe frostbite.
- Decompression in divers or astronauts can cause the ‘bends’ – a potentially fatal condition when nitrogen bubbles form in the bloodstream.
Characteristics:
- Nitrogen is a colorless, odorless, tasteless, diatomic and generally inert gas at standard temperature and pressure.
- At atmospheric pressure, nitrogen is liquid between 63 K and 77 K.
- Liquids colder than this are considerably more expensive to make than liquid nitrogen is.
Uses of Nitrogen
- Nitrogen is used to produce ammonia (Haber process) and fertilizers, vital for current food production methods. It is also used to manufacture nitric acid (Ostwald process).
- In enhanced oil recovery, high pressure nitrogen is used to force crude oil that would otherwise not be recovered out of oil wells. Nitrogen’s inert qualities find use in the chemical and petroleum industries to blanket storage tanks with an inert layer of gas.
- Liquid nitrogen is used as a refrigerant. Superconductors for practical technologies should ideally have no electrical resistance at temperatures higher than 63 K because this temperature is achievable relatively cheaply using liquid nitrogen. Lower temperatures come with a much higher price tag.
- While elemental nitrogen is not very reactive, many of nitrogen’s compounds are unstable. Most explosives are nitrogen compounds – gun powder (based on potassium nitrate), nitroglycerin, trinitro-toluene (TNT), nitrocellulose (gun cotton) nitroglycerin and ammonium nitrate are a few examples.
- Oxides naturally form in steel during welding and these weaken the weld. Nitrogen can be used to exclude oxygen during welding, resulting in better welds.
- In the natural world, the nitrogen cycle is of crucial importance to living organisms. Nitrogen is taken from the atmosphere and converted to nitrates through lightning storms and nitrogen fixing bacteria. The nitrates fertilize plant growth where the nitrogen becomes bound in amino acids, DNA and proteins. It can then be eaten by animals. Eventually the nitrogen from the plants and animals returns to the soil and atmosphere and the cycle repeats.
