Atomic mass units: Difference between revisions
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(New page: The Atomic Mass Unit is defined as the twelfth part of the mass of a C<math>_{12}</math> atom. Hence, it is approximately equal to the mass of a proton. Elements are asigned masses in thes...) |
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The Atomic Mass Unit is defined as the twelfth part | The Atomic Mass Unit is defined as the twelfth part | ||
of the mass of a C<math>_{12}</math> atom. Hence, | of the mass of a C<math>_{12}</math> atom. | ||
This is <math>1.66054\times10^{-27} </math> kilograms | |||
in SI units. | |||
Hence, | |||
it is approximately equal to the mass of a proton. | it is approximately equal to the mass of a proton. | ||
Elements are asigned masses in these units which are | Elements are asigned masses in these units which are | ||
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Here is a list of masses of elements and compounds in amus: | Here is a list of masses of elements and compounds in amus: | ||
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| Compound/element || mass in amu | | Compound/element || mass in amu | ||
Revision as of 11:52, 25 October 2007
The Atomic Mass Unit is defined as the twelfth part of the mass of a C atom. This is kilograms in SI units. Hence, it is approximately equal to the mass of a proton. Elements are asigned masses in these units which are not integer numbers. This is because neutrons and protons have slightly different masses, because nuclear binding forces cause the total mass of a nucleum to be less than that of the sum of its constituents, and, mainly, because of the appearance of natural isotopes. Thus, Potassium has a mass of 39.10 mainly because of natural K isotopes.
Here is a list of masses of elements and compounds in amus:
| Compound/element | mass in amu |
| Ar | 39.95 |
| Xe | 131.29 |
| CO2 | 44.01 |
| H2O, water | 18.02 |
| N2 | 28.01 |