Nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. It was first discovered and isolated by Scottish physician Daniel Rutherford in 1772. Although Carl Wilhelm Scheele and Henry Cavendish had independently done so at about the same time, Rutherford is generally accorded the credit because his work was published first. The name nitrogène was suggested by French chemist Jean-Antoine-Claude Chaptal in 1790 when it was found that nitrogen was present in nitric acid and nitrates. Antoine Lavoisier suggested instead the name azote, from the Ancient Greek: ἀζωτικός "no life", as it is an asphyxiant gas; this name is used instead in many languages, such as French, Italian, Russian, Romanian, Portuguese and Turkish, and appears in the English names of some nitrogen compounds such as hydrazine, azides and azo compounds.
Nitrogen is the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at about seventh in total abundance in the Milky Way and the Solar System. At standard temperature and pressure, two atoms of the element bind to form dinitrogen, a colourless and odorless diatomic gas with the formula N2. Dinitrogen forms about 78% of Earth's atmosphere, making it the most abundant uncombined element. Nitrogen occurs in all organisms, primarily in amino acids (and thus proteins), in the nucleic acids (DNA and RNA) and in the energy transfer molecule adenosine triphosphate. The human body contains about 3% nitrogen by mass, 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.
Many industrially important compounds, such as ammonia, nitric acid, organic nitrates (propellants and explosives), and cyanides, contain nitrogen. The extremely strong triple bond in elemental nitrogen (N≡N), the second strongest bond in any diatomic molecule after carbon monoxide (CO),[3] dominates nitrogen chemistry. This causes difficulty for both organisms and industry in converting N2 into useful compounds, but at the same time means that burning, exploding, or decomposing nitrogen compounds to form nitrogen gas releases large amounts of often useful energy. Synthetically produced ammonia and nitrates are key industrial fertilisers, and fertiliser nitrates are key pollutants in the eutrophication of water systems.
Apart from its use in fertilisers and energy-stores, nitrogen is a constituent of organic compounds as diverse as Kevlar used in high-strength fabric and cyanoacrylate used in superglue. Nitrogen is a constituent of every major pharmacological drug class, including 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 metabolizing into nitric oxide. Many notable nitrogen-containing drugs, such as the natural caffeine and morphine or the synthetic amphetamines, act on receptors of animal neurotransmitters.
Properties of Nitrogen
Nitrogen makes up the bulk of earth's atmosphere: 78.1 percent by volume. It is so inert at standard temperature and pressure that it was termed "azote" (meaning "without life") in Antoine Lavoisier's Method of Chemical Nomenclature. Nevertheless, nitrogen is a vital part of food and fertilizer production and a constituent of the DNA of all living things.
Characteristics
Nitrogen gas (chemical symbol N) is generally inert, nonmetallic, colorless, odorless and tasteless. Its atomic number is 7, and it has an atomic weight of 14.0067. Nitrogen has a density of 1.251 grams/liter at 0 C and a specific gravity of 0.96737, making it slightly lighter than air. At a temperature of -210.0 C (63K) and a ressure of 12.6 kilopascals, nitrogen reaches its triple point (the point an element can exist in gaseous, liquid and solid forms simultaneously).
Other States
At temperatures below nitrogen's boiling point of -195.79 C (77K), gaseous nitrogen condenses into liquid nitrogen, a fluid that resembles water and remains odorless and colorless. Nitrogen solidifies at a melting point of -210.0 C (63K) into a fluffy solid resembling snow.
Molecular Bonding
Nitrogen forms trivalent bonds in most compounds. In fact, molecular nitrogen exhibits the strongest possible natural triple bond due to the five electrons in the outer shell of the atom. This strong triple bond, along with nitrogen's high electronegativity (3.04 on the Pauling scale), explains its nonreactivity.
Uses
Nitrogen gas is useful in industrial and production settings due to its abundance and nonreactivity. In food production, nitrogen gas suppression systems can extinguish fires without fear of contamination. Iron, steel and electronic components, which are sensitive to oxygen or moisture, are produced in a nitrogen atmosphere. Nitrogen gas is commonly combined with hydrogen gas to produce ammonia.
Potential
In 2001, "Nature" reported that Carnegie Institution of Washington scientists were able to transform gaseous nitrogen into a solid state by subjecting the gaseous form to intense pressure. The researchers pressed a sample of nitrogen between two pieces of diamond with a force equivalent to 1.7 million times that of atmospheric air pressure, transforming the sample into a clear solid resembling ice, but with a crystal structure like that of diamond. At temperatures below -173.15°C (100K) the sample remained a solid when pressure was removed. When it reverts back to gaseous state nitrogen releases great amounts of energy, leading physics professor Dr. Richard M. Martin to speculate on its use as a rocket fuel.
कोई टिप्पणी नहीं:
एक टिप्पणी भेजें