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# Topic: Unified atomic mass unit

###### In the News (Thu 21 Mar 19)

 atomic mass unit Although not an SI unit, the unified atomic mass unit is accepted by the CGPM for use with SI. The mass of the unified atomic mass unit is determined experimentally. The mole and the unified atomic mass unit. www.sizes.com /units/atomic_mass_unit.htm   (1060 words)

 atomic mass - HighBeam Encyclopedia   (Site not responding. Last check: 2007-11-07) atomic mass the mass of a single atom, usually expressed in atomic mass units (amu). Each proton or neutron weighs about 1 amu, and thus the atomic mass is always very close to the mass number (total number of protons and neutrons in the nucleus). Atomic masses are usually determined by mass spectrography (see mass spectrograph). www.encyclopedia.com /doc/1E1-atomm1as.html   (230 words)

 Glossary of Terms in Quantities and units in Clinical Chemistry The atomic mass constant is equal to one unified atomic mass unit (11). The henry is the SI unit for inductance (13). SI unit for solid angle, equal to the solid angle extending from the centre of a sphere to span an area on its surface equal to the square of the radius (13). www.labinfo.dk /English/Documents/glossary.htm   (8167 words)

 WWWolfe Atoms, Elements, and the Periodic Table An atom with a mass one-fourth the mass of Atomic masses of the elements are decimal numbers (e.g., Al, 26.9815; S, 32.06; V, 50.942; etc.) because a large percent of the naturally occurring elements exists as a mixture of isotopes. The atomic mass of B is obtained by calculating the average mass of its isotopes. www.mindspring.com /~drwolfe/Atoms_elements.htm   (5165 words)

 Units: A In metric countries the unit corresponding to the acre is the hectare, which is 10,000 square meters (the area of a square 100 meters on each side). One astronomical unit equals the "average" distance from the center of the Earth to the center of the Sun (mathematically, it is the length of the semimajor axis of the Earth's elliptical orbit, which is the ordinary average of the Earth's minimum and maximum distances from the Sun). the unit of mass used by chemists and physicists for measuring the masses of atoms and molecules. www.unc.edu /~rowlett/units/dictA.html   (5441 words)

 Units: U For components of blood, one unit is the amount of that substance that would normally be found in one unit of whole blood. The unit call is a dimensionless "unit" representing a traffic density of 100 call-seconds per hour, or 1/36 erlang. A unit magnetic pole repels an identical pole at a distance of one centimeter in a vacuum with a force of one dyne. www.unc.edu /~rowlett/units/dictU.html   (1315 words)

 PowerPedia:Kilogram - PESWiki The kilogram was originally defined as the mass of one litre of pure water at a temperature of 3.98 degrees Celsius and standard atmospheric pressure. Since 1889, the SI system defines the unit to be equal to the mass of the international prototype of the kilogram, which is made from an alloy of platinum and iridium of 39 mm height and diameter, and is kept at the Bureau International des Poids et Mesures (International Bureau of Weights and Measures). An object of mass 1 kg at the surface of the Earth will be subjected to a gravitational force of approximately 9.80665 newtons (the SI unit of force). peswiki.com /index.php/PowerPedia:Kilogram   (1047 words)

 The Application of an Activity Relating to the Determination of Avogadro's Number in a Class of First-Year Science ... In addition, they calculated the conversion factor that relates the (unified) atomic mass unit to grams by using the definition of the amu and the mass of a single atom of carbon-12 in grams. The amu is a standard mass unit that is equal to one-twelfth the mass of a neutral atom of the carbon-12 isotope. For example, according to the base of J. Berzelius' atomic mass scale, an atomic mass unit is one-hundredth of the mass of a single oxygen atom [3]. chemeducator.org /sbibs/s0009001/spapers/910017ms.htm   (1926 words)

 The Unified Code for Units of Measure The second is a metric unit because it is a part of the SI basis, although it used to be part of a series of customary units (originating in the Babylonian era). The semantics of The Unified Code for Units of Measure is defined by the algebraic operations of multiplication, division and exponentiation between units, by the equivalence relations of equality and commensurability of units, and by the multiplication of a unit with a scalar. Units were taken from nature: anatomical structures (e.g., arm, foot, finger), botanical objects (e.g., grains of various sorts, rod), or processes of everyday life (e.g., amount of land one could plow in a morning, the length of 1000 steps, an hour of walking, etc.). aurora.rg.iupui.edu /~schadow/units/UCUM/ucum.html   (8920 words)

 Basic Atomic Theory for Chemistry The mass of hydrogen that combines with 1.00 g of nitrogen to form three of these compounds are: urea, 0.1428 g; ammonia, 0.0714 g; ammonium chloride, 0.2857 g. An alternative way of examining the behavior of individual atomic particles became evident in 1899, when J.J. Thomson, whose work on "cathode rays" had revealed that the atoms has internal components of its own, showed that the charged particles resulting from their break-up could be deflected by externally-applied magnetic and electrostatic fields. The unified atomic mass unit is defined as 1/12 of the mass of one atom of carbon-12. www.chem1.com /acad/webtext/intro/AT.html   (5372 words)

 Talk:Mass - Mass Spectrometry Terms   (Site not responding. Last check: 2007-11-07) In mass spectrometry it is more common to use the unified atomic mass unit u, which is better called Dalton Da. In spite of their name, mass spectrometers do not measure the mass of ions, but the mass/charge (m/q) of ions. Because (1) protons and neutrons have simillar masses, and (2) the nucleons dominate the total mass, the total mass of particles is dominated by the number of nucleons. www.msterms.com /wiki/index.php?title=Talk:Mass   (260 words)

 base and derived units of the international system The kelvin, unit of thermodynamic temperature, is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water. the unit of atomic mass is equal to 1/12 of the mass of an atom of the nuclide 12C From the observation of the preceding definitions one note the tendency to duty release the units of fundamental measure from the members.tripod.com /units_of_measure/un-fon_e.htm   (564 words)

 BIPM - Table 7 The values in SI units of all units in this table, except the astronomical unit, are taken from the 2002 CODATA set of recommended values of the fundamental physical constants, P.J. Mohr and B.N. Taylor, Rev. The dalton (Da) and the unified atomic mass unit (u) are alternative names (and symbols) for the same unit, equal to 1/12 times the mass of a free carbon 12 atom, at rest and in its ground state. The dalton is often combined with SI prefixes, for example to express the masses of large molecules in kilodaltons, kDa, or megadaltons, MDa, or to express the values of small mass differences of atoms or molecules in nanodaltons, nDa, or even picodaltons, pDa. www.bipm.org /en/si/si_brochure/chapter4/table7.html   (329 words)

 BIPM - accepted for use Natural units (n.u.) and atomic units (a.u.) are used only in their own special fields of particle and atomic physics, and quantum chemistry, respectively. Although the use of SI units is to be preferred for reasons already emphasized, authors who see a particular advantage in using these non-SI units should have the freedom to use the units that they consider to be best suited to their purpose. Since, however, SI units are the international meeting ground in terms of which all other units are defined, those who use units from Tables 8 and 9 should always give the definition of the units they use in terms of SI units. www.bipm.org /en/si/si_brochure/chapter4/4-1.html   (1367 words)

 Atomic Weight - Succeed in Physical Science The atomic weight of an atom was originally defined as the sum of the number of its protons and its neutrons. The atomic weight or mass of an element is approximately the sum of the number of protons and neutrons in the nucleus. This value is not a whole number because the atomic weights of the proton and neutron are not exactly 1, the additional effect of energy-mass factor of fission and fusion reactions, and the averaging of the weights of isotopes. www.school-for-champions.com /science/atomic_weight.htm   (1146 words)

 Richard P. Feynman on Physical Units - Numericana The mass of an atom, from a chemist's point of view, is given by the mass of a mole of these atoms. For example, the mass of carbon-12 is called 12 "atomic mass units" (u), because a mole of carbon-12 "weighs" 12 grams (or rather "has 12 grams of mass"). It is based on the "unified" definition of the "atomic mass unit" (amu) as 1/12 the mass of a Carbon-12 atom, which was adopted at the 10th General Assembly of the International Union of Pure and Applied Physics (Ottawa, 1960) and subsequently by the International Union of Pure and Applied Chemistry in 1961. home.att.net /~numericana/answer/feynman.htm   (2239 words)

 IUPAP: C2: Report 2005 These evaluations of experimental data (and sometimes estimates from extrapolation of the surface of masses for values that are not available from experiment) on atomic masses have been carried out since the early 1950’s at intervals of approximately 4 years. The goal of the evaluation is to produce a self-consistent, recommended set a atomic masses for use by the scientific community and others. After considerable discussion it was agreed that both units, u and D, should be allowed official use and that the situation be reexamined in the future to evaluate whether the use of these units in the scientific community would suggest the selection of one of these names over the other. www.iupap.org /commissions/c2/reports/ga-05.html   (1566 words)

 [No title] Postulates of Kinetic Theory A large number of molecules or atoms of mass m are constantly moving in random directions with a particular velocity distribution. Mass Today the atomic mass scale is set by assigning a single atom of the common isotope  (12C) of carbon a value of 12.0000u. The number of grams in one mole is the same as the molecular (or atomic) mass of the substance. home.insightbb.com /~phys1/notes/notes13.doc   (1065 words)

 Physics reference: SI units The most commonly-used composition of more fundamental units that is described as composing the unit. This is a polynomial-like combination of the eight elementary and supplementary units: kg, m, s, A, K, rad, cd, and sr. The unit ohm is actually represented with a Greek capital letter Omega, but is represented as a capital letter O throughout these pages. www.alcyone.com /max/reference/physics/units.html   (368 words)

 Atomic Masses Mass excess values in MeV where the Mass excess = [M (in a.m.u.) - A], and 1 a.m.u.(atomic mass unit) = M(12C)/12. Mass Predictions by Modified Ensemble Averaging, E. Comay, I. Kelson, and A. Masses of Atomic Nuclei in the Infinite Nuclear Matter Model, L. Satpathy and R.C. Nayak. ie.lbl.gov /toimass.html   (390 words)

 SBF Glossary: U to UIUC Unified in 1961, as explained at the amu entry. In particular, ``U'' is a standard unit of measure for the heights of computer enclosures and the appropriate unit for specifying the size of units to be mounted in a standard (EIA standard SE-102) equipment rack. There are three screw-holes in the rail per cluster, and if your unit is only one U tall, you are well-advised to use four screws: top and bottom on each side. www.plexoft.com /SBF/U.html   (7416 words)

 Dalton - Mass Spectrometry Terms   (Site not responding. Last check: 2007-11-07) A non-SI unit of mass (symbol Da) that is equal to the unified atomic mass unit. This is a provisional recommendation for the term Dalton from the Mass Spectrometry Terms and Definitions Project. Non-SI unit of mass (symbol Da), equal to the unified atomic mass unit (atomic mass constant). www.msterms.com /wiki/index.php?title=Dalton   (96 words)

 JCE 2004 (81) 800 [Jun] SI for Chemists: Persistent Problems, Solid Solutions; SI Basic Units: The Kilogram and the Mole On the other hand, if Karol’s statement is meant to be a new definition of the “gram”, that should have been stated explicitly and the procedure for realizing the “new gram” in terms of a counted number of atoms should have been described and/or referenced. The problem with redefinition of the kilogram is not the absence of “an integer”; rather it is the difficulty in comparing macroscopic masses with microscopic masses and in determining the mass of large (1 kg) masses with adequate precision. For example, in ref 1 masses of many nuclides are given, in u or Da, with an uncertainty of a few parts in 1p9 (2), and some a few parts in 1p10; in contrast, masses of the electron, proton, and neutron are given, in kg, with an uncertainty of a few parts in 1p6. jchemed.chem.wisc.edu:8000 /journal/issues/2004/Jun/abs800_2.html   (802 words)

 The Unified Code for Units of Measure The Unified Code for Units of Measure intends to provide a single coding system for units that is complete, free of all ambiguities, and that assigns to each defined unit a concise semantics. The Unified Code for Units of Measures is very stable in content and has already been adopted by some standard organizations such as DICOM, HL7 and has been referenced as best practice by the Open Geospatial Consortium in their Web Map Service (WMS) and Geography Markup Language (GML) implementation specifications. Fortunately these units are rather rare in everyday use in trade and medicine, however, we must urge everyone to regenerate their tables, dictionaries, and knowledge bases, and check their data immediately based on this corrected release of The Unified Code for Units of Measure. aurora.rg.iupui.edu /~schadow/units/UCUM   (1500 words)

 IUPAP: IU14. Report to the 2005 General Assembly General Assembly of the I.U.P.A.P. in 1960) of the exact number 12 as the relative nuclidic mass of the carbon isotope of mass number 12, had been made jointly with IUPAC, and it would perhaps be fitting to co-ordinate similarly the current proposal about the dalton. In the short term the proposed change simply endorses the present reality that both the atomic mass unit and Dalton are in use. IUPAP should endorse the use of both names, dalton (Da) and unified atomic mass unit (u) for the atomic mass unit and strongly recommends waiting for an extended period to see which physicists and others prefer to use before making any further decisions. www.iupap.org /commissions/interunion/iu14/ga-05.html   (917 words)

 Chapter 30 Objectives Determine the number of neutrons in a nuclide of known atomic number and mass number. Calculate the energy equivalent in MeV of an atomic mass unit. Given a table of nuclear masses, calculate the binding energy of a nucleus and the binding energy per nucleon. www.cbpu.com /swangl/chapter30.htm   (226 words)

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