hy the relative atomic mass is never a whole number
Because there are different isotopes of the elements. The atomic weight is the average based on the proportions that they occur in naturally. For example, hydrogen comes with a single proton, a proton + a neutron, and a proton plus two neutrons. [ The isotopes with the neutrons occur in very small amounts so the average weight is slightly greater than 1. According to Wikipedia, atomic masses were arbitrarily based on the most prevalent isotope of oxygen being defined as the integer 16 by physicists, and the mean mass of all isotopes of oxygen was assigned the integer 16 by chemists. Again,
according to the same article, this arbitrary definition has now been changed to the integer 12 for carbon-12 isotope.
In any case, only one atomic mass can be an integer because of the difference in mass between a proton and neutron, and the fact that the sum of the particle masses for any isotope is not equal to the mass of the isotope. ]
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Asked 10/23/2011 7:26:42 AM
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