Science / Periodic Table of Elements / Nitrogen (N): Atomic number: 7, Atomic mass: 14.0067 g.mol -1, Electronegativity: 3.0, Density: 1.25*10-3 g.cm-3 at 20°C, Melting point: -210 °C, Boiling point: -195.8 °C, Vanderwaals radius: 0.092 nm, Ionic radius: 0.171 nm (-3) ; 0.011 (+5) ; 0.016 (+3), Isotopes: 4, Electronic shell: [ He ] 2s22p3, Energy of first ionisation: 1402 kJ.mol -1, Energy of second ionisation: 2856 kJ.mol -1, Energy of third ionisation: 4578 kJ.mol -1, Discovered by: Rutherford in 1772. Nitrogen is a common normally colourless, odourless, tasteless and mostly diatomic non-metal gas. It has five electrons in its outer shell, so it is trivalent in most compounds. Applications: The greatest single commercial use of nitrogen is as a component in the manufacture of ammonia, subsequently used as fertilizer and to produce nitric acid. Liquid nitrogen (often referred to as LN2) is used as a refrigerant for freezing and transporting food products, for the preservation of bodies and reproductive cells (sperm and eggs), and for stable storage of biological samples. Nitric acid salts include some important compounds, for example potassium nitrate, nitric acid, and ammonium nitrate. Nitrated organic compounds, such as nitro-glycerine and trinitrotoluene, are often explosives. Nitrogen in the environment: Nitrogen constitutes 78 percent of Earth's atmosphere and is a constituent of all living tissues. Nitrogen is an essential element for life, because it is a constituent of DNA and, as such, is part of the genetic code. Nitrogen molecules occur mainly in air. In water and soils nitrogen can be found in nitrates and nitrites. All of these substances are a part of the nitrogen cycle, and there are all interconnected. Humans have changed natural nitrate and nitrite proportions radically, mainly due to the application of nitrate-containing manures. Nitrogen is emitted extensively by industrial companies, increasing the nitrate and nitrite supplies in soil and water as a consequence of reactions that take place in the nitrogen cycle. Nitrate concentrations in drinking water will greatly increase due to this.
Science / Genetics / Nitrogenous Base: A nitrogen-containing molecule having the chemical properties of a base. Dna contains the nitrogenous bases adenine (a), guanine (g), cytosine (c), and thymine (t). MORE
Science / Marine Biology / Nitrogen Fixation: The conversion of gaseous nitrogen to nitrate by specialized bacteria. MORE