Angstrom Definition (Physics and Chemistry)

Angstrom Definition (Physics and Chemistry) An angstrom or à ¥ngstrà ¶m  is a unit of length used to measure very small distances. One angstrom is equal to  10−10  m  (one ten-billionth of a  meter  or 0.1  nanometers). Although the unit is recognized world-wide, it is not an International System  (SI) or metric unit.The symbol for angstrom is Ã…, which is a letter in the Swedish alphabet.1 Ã… 10-10 meters. Uses of the Angstrom The diameter of an atom is on the order of 1 angstrom, so the unit is particularly handy when referring to the atomic and ionic radius or size of molecules and spacing between planes of atoms in crystals. The covalent radius of atoms of chlorine, sulfur, and phosphorus are about one angstrom, while the size of a hydrogen atom is about half of an angstrom. The angstrom is used in solid state physics, chemistry, and crystallography. The units is used to cite wavelengths of light, chemical bond length, and the size of microscopic structures using the electron microscope. X-ray wavelengths may be given in angstroms, as these values typically range  1–10 Ã…. Angstrom History The unit is named for Swedish physicist Anders Jonas  Ãƒâ€¦ngstrà ¶m, who used it to produce a chart of the wavelengths of electromagnetic radiation in sunlight in 1868. His use of units made it possible to report the wavelengths of visible light (4000  to  7000  Ãƒâ€¦) without having to use decimals or fractions. The chart and unit became widely used in solar physics, atomic spectroscopy, and other sciences that deal with extremely small structures. Although the angstrom is  10−10  meters, it was precisely defined by its own standard because it is so small. The error in the meter standard was larger than the anstrom unit! The 1907 definition of the angstrom was the wavelength of the red line of cadmium set to be  6438.46963 international à ¥ngstrà ¶ms. In 1960, the standard for the meter was redefined in terms of spectroscopy, finally basing the two units on the same definition. Multiples of the Angstrom Other units based on the angstrom are the micron (104  Ãƒâ€¦) and the millimicron (10 Ã…). These units are used to measure thin film thicknesses and molecular diameters. Writing the Angstrom Symbol Although the symbol for the angstrom is easy to write on paper, some code is needed to produce it using digital media. In older papers, the abbreviation A.U. was sometimes used. Methods of writing the symbol include: Typing the symbol U212B or U00C5 in UnicodeUsing the symbol #8491 or #197 in HTMLUsing the code Aring; in HTML Sources International Bureau of Weights and Measures (2006). The International System of Units (SI) (8th ed.).  p. 127. ISBN 92-822-2213-6.Wells, John C. (2008). Longman Pronunciation Dictionary (3rd ed.). Longman, ISBN 9781405881180.