That there was a fraction of air that did not support combustion was well known to the late 18th century chemist. Nitrogen ( Latin nitrogenium, where nitrum (from Greek nitron) means "native soda" (see niter), and genes means "forming") is formally considered to have been discovered by Daniel Rutherford in 1772, who called it noxious air or fixed air. This visible blue air glow (seen in the polar aurora and in the re-entry glow of returning spacecraft) typically results not from molecular nitrogen, but rather from free nitrogen atoms combining with oxygen to form nitric oxide (NO).
Nitrogen also makes a contribution to visible air glow from the Earth's upper atmosphere, through electron impact excitation followed by emission. For similar reasons, pure molecular nitrogen lasers typically emit light in the far ultraviolet range. Nitrogen absorption leads to significant absorption of ultraviolet radiation in the Earth's upper atmosphere as well as in the atmospheres of other planetary bodies. This is associated with electronic transitions in the molecule to states in which charge is not distributed evenly between nitrogen atoms. Significant absorption occurs at extreme ultraviolet wavelengths, beginning around 100 nanometers. Molecular nitrogen ( 14N 2) is largely transparent to infrared and visible radiation because it is a homonuclear molecule and thus has no dipole moment to couple to electromagnetic radiation at these wavelengths. The molecular nitrogen in Earth's atmosphere is 0.73% comprised of the isotopologue 14N 15N and almost all the rest is 14N 2. These reactions almost always result in 15N enrichment of the substrate and depletion of the product.
Biologically-mediated reactions (e.g., assimilation, nitrification, and denitrification) strongly control nitrogen dynamics in the soil. Of the ten isotopes produced synthetically, 13N has a half life of nine minutes and the remaining isotopes have half lives on the order of seconds or less. By far the most common is 14N (99.634%), which is produced in the CNO cycle in stars and the remaining is 15N. There are two stable isotopes of nitrogen: 14N and 15N. It is a large component of animal waste (for example, guano), usually in the form of urea, uric acid, and compounds of these nitrogenous products. Nitrogen is present in all living tissues as proteins, nucleic acids and other molecules. Molecular nitrogen is a major constituent of Titan's thick atmosphere, and occurs in trace amounts of other planetary atmospheres. Nitrogen is the largest single component of the Earth's atmosphere (78.084% by volume, 75.5% by weight).ġ4Nitrogen is created as part of the fusion processes in stars.Ĭompounds that contain this element have been observed by astronomers, and molecular nitrogen has been detected in interstellar space by David Knauth and coworkers using the Far Ultraviolet Spectroscopic Explorer. Liquid nitrogen, a fluid resembling water, but with 81% of the density, is a common cryogen. Molecular nitrogen condenses at 77 K at atmospheric pressure and freezes at 63 K.
The resulting difficulty of converting (N 2) into other compounds, and the relative ease (and associated high energy release) of converting nitrogen compounds into elemental N 2, have dominated the role of nitrogen in both nature and human economic activities. The triple bond in molecular nitrogen (N 2) is one of the strongest in nature. It has five electrons in its outer shell and is therefore trivalent in most compounds. Nitrogen is a non-metal, with an electronegativity of 3.0. Notable characteristics of elemental nitrogen Many industrially important compounds, such as ammonia, nitric acid, and cyanides, contain nitrogen. Nitrogen is a constituent element of all living tissues and amino acids. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78.08% percent of Earth's atmosphere. Nitrogen ( IPA: /ˈnʌɪtrə(ʊ)dʒən/) is a chemical element which has the symbol N and atomic number 7 in the periodic table.
0 kommentar(er)
