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Relative atomic mass

  1. Jan 12, 2008 #1


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    1 u = 1/12 of the mass of a neutral carbon atom with nuclear charge 6 and mass number 12,

    1 u = 1/12 * 12.000000 /NA * 0.001

    where NA is avogadro's number.

    I wonder is it that the scientists purposely make one mole of carbon-12 to be just 12.00000g?

    I want to ask is it when the relative atomic mass of oxygen-16 is 15.99491, then the mass of the oxygen-16 atom is 15.99491 * 1u.?
  2. jcsd
  3. Jan 12, 2008 #2


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    Science Advisor
    Gold Member

    Well, Avogadro's number is, by definition, equal to the number of atoms in 12 gram of carbon-12.
    So, yes, it is on purpose.
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