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Topic: Atomic mass unit


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  Atomic mass unit - Biocrawler   (Site not responding. Last check: 2007-10-09)
The relative atomic mass is measured with a mass spectrometer.
Before 1961, the physical atomic mass unit was defined as 1/16 of the mass of one atom of oxygen-16, while the chemical atomic mass unit was defined as 1/16 of the average mass of an oxygen atom (taking the natural abundance of the different oxygen isotopes into account).
Both units are slightly smaller than the unified atomic mass unit, which was adopted by the International Union of Pure and Applied Physics in 1960 and by the International Union of Pure and Applied Chemistry in 1961.
www.biocrawler.com /encyclopedia/Amu   (650 words)

  
 Atomic mass unit - Encyclopedia, History, Geography and Biography   (Site not responding. Last check: 2007-10-09)
It is defined to be 1/12 of the mass of one atom of carbon-12.
Chemical element masses, as expressed in u, would therefore all be close to whole number values (within 2% and usually within 1%) were it not for the fact that atomic weights of chemical elements are averaged values of the various stable isotope masses in the abundances which they naturally occur.
Mass spectrometry looking at isotope ratios is most often used by archaeologists to determine the ages of old man-made objects based upon the isotopic proportions of carbon.
www.arikah.net /encyclopedia/KDa   (677 words)

  
 Glossary [A-Bomb to AWACS] | atomicarchive.com
The atomic bomb is an explosive device that depends upon the release of energy in a nuclear reaction known as fission, which is the splitting of atomic nuclei.
A relative mass unit based on the atomic weight of carbon 12, which is taken to be 12; the atomic mass of hydrogen is 1.008 amu.
Atomic number is often symbolized with the letter Z and is shown as a numerical subscript to the left of its chemical symbol.
www.atomicarchive.com /Glossary/Glossary1.shtml   (1027 words)

  
 CHEM 0010 Unit
The unit of atomic mass of an atom is atomic mass unit.
the atomic mass of ONE magnesium atom = 24.3050 amu
the atomic mass of ONE copper atom= 63.546 amu.....
nobel.scas.bcit.ca /chem0010/unit3/3.5_atomicMass.htm   (215 words)

  
 Highbeam Encyclopedia - Search Results for atomic mass unit   (Site not responding. Last check: 2007-10-09)
atomic mass unit ATOMIC MASS UNIT [atomic mass unit] or amu, in chemistry and physics, unit defined as exactly 1/12 the mass of an atom of carbon-12, the isotope of carbon with six protons and six neutrons in its nucleus.
atomic weight ATOMIC WEIGHT [atomic weight] mean (weighted average) of the masses of all the naturally occurring isotopes of a chemical element, as contrasted with atomic mass, which is the mass of any individual isotope.
It is based on a unit of length, called the meter (m), and a unit of mass, called the kilogram (kg).
www.encyclopedia.com /printablenew/43149.html   (617 words)

  
 Atomic Theory   (Site not responding. Last check: 2007-10-09)
The mass of Carbon-12 is defined as 12.000000 atomic mass units (amu).
The atomic volume of an element is the relative atomic mass of the element divided by is density.
The atomic weight of an element is its relative atomic mass, which is the ratio of the average mass per atom of the naturally occurring form of an element to one twelfth (i.e.
www.ucc.ie /ucc/depts/chem/dolchem/html/dict/atom.html   (1217 words)

  
 Glossary
The atomic mass is found on the periodic table below the symbol of the element in each box and represents the average mass of an atom.
Then, the atomic mass is the average mass for all the isotopes of the element.
The atomic mass unit is defined as exactly 1/12th the mass of a carbon-12 atom, or 1.66057 x 10 -24 g.
www.chem.wisc.edu /areas/cur_dev/CurrRef/Glossary/Glossary.html.old   (1934 words)

  
 Introductory Terms, Page 2
one atomic mass unit is equal to 1/12th the mass of one atom of Carbon-12.
Atomic weight is the decimal number most commonly associated with each element's symbol on the Periodic Chart.
The values for the atomic weights of the elements are calculated by summing the products of the different individual Isotope Masses multiplied by the decimal equivalent of their percent of abundance values.
www.bcpl.net /~kdrews/introterms/intro2.html   (823 words)

  
 Atomic Mass
One atomic mass unit (amu) is 1/12 the mass of one atom of
An atomic mass (average atomic mass or atomic weight) found on the periodic chart is the weighted average mass of all the isotopes of an element.
A molar mass of an element is the mass of one mole of average atoms of a given element in grams.
www.mc.cc.md.us /faculty/~plastas/public_html/atommass.htm   (274 words)

  
 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.
Thus the two amu’s clearly diverged: one based on one-sixteenth of the average mass of the oxygen atoms in the chemist’s laboratory, and the other based on one-sixteenth of the mass of an atom of a particular isotope of oxygen.
www.sizes.com /units/atomic_mass_unit.htm   (1060 words)

  
 unit01-sect01-les02-lessonc   (Site not responding. Last check: 2007-10-09)
Atomic masses are relative units as opposed to measurable units.
The atomic mass of this element cannot be one value or the other - it has to be a combination of the two.
Average atomic mass is the weighted average of the atomic masses of the isotopes of an element.
www.cdli.ca /courses/chem2202/unit01/section01/lesson02/3-lesson-c.htm   (232 words)

  
 atomic mass unit Comparison Table   (Site not responding. Last check: 2007-10-09)
The masses of atoms and molecules are generally given in atomic mass units.
These units are based on a scale in which the mass of carbon 12 is taken to be 12.
Atomic masses were originally given as atomic weights on a scale where the mass of the hydrogen atom was unity, later they were based on oxygen or oxygen 16; these scales have all been replaced by the carbon 12 scale.
www.site.uottawa.ca:4321 /astronomy/atomicmassunit_table.html   (109 words)

  
 Atomic mass unit : Amu   (Site not responding. Last check: 2007-10-09)
The atomic mass unit, also called the dalton after the chemist John Dalton, is a small unit of mass used to express atomic masses and molecular masses.
Another reason the unit is used is that it is much easier to compare masses of atoms and molecules (determine relative masses) than to measure their absolute masses.
For example, the molecular mass of water is 18.01508 amu, and this means that one mole of water weighs 18.01508 grams, or conversely that 1 gram of water contains N
www.termsdefined.net /am/amu.html   (420 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)

  
 Talk:M/z - Mass Spectrometry Terms
Using the correct SI units (http://en.wikipedia.org/wiki/International_system_of_units), the mass/charge ratio sould be indicated in kg/C (kilograms/Coulombs).
Instead the mass is indicated in the Atomic Mass Unit u and the charge is indicated in multiples of the elementary charge (http://en.wikipedia.org/wiki/Elementary_charge) e.
Hence the correct labling of "mass spectra" would be m/q (u/e) where m is the symbol for mass, q the symbol for charge, u the unit of mass in atomic mass units (also called Dalton, Da), and e the unit of charge in elementary charge units.
www.msterms.com /wiki/index.php?title=Talk:M/z   (755 words)

  
 Atomic mass unit Biography,info   (Site not responding. Last check: 2007-10-09)
It is defined to be one twelfth of the mass of a carbon-12 nucleus.
The unified atomic mass unit, or dalton, is not an SI unit of mass, although it is accepted for use with SI under either name.
of the mass of one atom of oxygen-16 as his unit.
music.musictnt.com /biography/sdmc_Amu   (606 words)

  
 Weight/Mass Converter
Convert between different weight/mass units like kilogram, atomic mass unit, pound, ounce, etc. The SI base unit for mass is kilogram (kg).
Kilogram is the SI base unit for mass.
1 amu = 1/12 of the mass of a carbon-12 atom.
www.convertunit.com /weight_mass_converter.php   (184 words)

  
 Atomic Mass Units   (Site not responding. Last check: 2007-10-09)
Another way is to define a new mass unit and say that it is equal to the mass of one hydrogen atom.
That unit is called the atomic mass unit (amu) and is defined, for the moment, as the mass of one hydrogen atom.
Using the current standard, the actual definition of an atomic mass unit is that it is 1/12th of the mass of one atom of the carbon-12 isotope.
dl.clackamas.cc.or.us /ch104-04/atomic1.htm   (244 words)

  
 atomic mass unit — FactMonster.com
atomic mass unit or amu,in chemistry and physics, unit defined as exactly 1/12 the mass of an atom of carbon-12, the
atomic weight - atomic weight, mean (weighted average) of the masses of all the naturally occurring isotopes of a...
atomic mass - atomic mass, the mass of a single atom, usually expressed in atomic mass units (amu).
www.factmonster.com /ce6/sci/A0805234.html   (143 words)

  
 Unit 2   (Site not responding. Last check: 2007-10-09)
Atomic # - the # of protons in an atom; used to identify the element
Isotopes - elements that have the same atomic # but different atomic masses due to a difference in the # of neutrons in the nucleus.
Atomic mass is really a weighted average of all of the isotopes that exist in nature for that element.
www.troy.k12.ny.us /thschemistry/unit2.html   (474 words)

  
 What is atomic mass unit? - a definition from Whatis.com - see also: AMU   (Site not responding. Last check: 2007-10-09)
An atomic mass unit (symbolized AMU or amu) is defined as precisely 1/12 the mass of an atom of carbon-12.
The mass of an atom in AMU is roughly equal to the sum of the number of protons and neutrons in the nucleus.
The AMU is used to express the relative masses of, and thereby differentiate between, various isotopes of elements.
whatis.techtarget.com /definition/0,,sid9_gci831527,00.html   (228 words)

  
 CHEM 0010 Unit
In section 3.5 we learned about atomic mass and the unit of amu was introduced.
It is important that you fully understand the concept of atomic mass unit.
The atomic mass of one atom has units of atomic mass unit, amu.
nobel.scas.bcit.ca /chem0010/unit7/7.3_atomicmass.htm   (216 words)

  
 Physikalisch-Technische Bundesanstalt (PTB) 1.24 Atomic Mass Unit
The kilogram is the only one of the seven SI base units (metre, kilogram, second, ampere, kelvin, mole, candela) that is not yet defined by an atomic or fundamental constant of physics, but by a material artefact, the international prototype of the kilogram.
Mass changes of the BIPM reference standards against the international prototype of the kilogram (similar drifts are observed for national prototypes).
The quotient: elementary charge multiplied by the mass flow and divided by the ion current (or: elementary charge e multiplied by the accumulated mass m and divided by the accumulated charge Q) has been measured as a function of the ion energy.
www.ptb.de /en/org/1/12/124/ionenex.htm   (693 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)

  
 Some detail on three different units for the mass of an atomic particle   (Site not responding. Last check: 2007-10-09)
There are two other ways to express the mass of atomic particles and the whole atom itself.
atomic mass units would for evermore be 12 unified atomic mass units or 12 u.
As you might suspect, it is only the carbon atom that has an exact whole number mass in the unified mass unit.
www.cdli.ca /courses/phys3204/unit03/section06/lesson01/6-popup-b.htm   (479 words)

  
 Nuclear Units
Nuclear masses are measured in terms of atomic mass units with the carbon-12 nucleus defined as having a mass of exactly 12 amu.
The number of protons is called the atomic number and determines the chemical element.
Nuclei of a given element (same atomic number) may have different numbers of neutrons and are then said to be different isotopes of the element.
hyperphysics.phy-astr.gsu.edu /hbase/nuclear/nucuni.html   (416 words)

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