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Why carbon-12?

Discussion in 'Science' started by gasheadruss, Apr 7, 2012.

  1. Can anyone tell me why carbon-12 is used as the standard to which the mass of all other atoms are compared?
    I'm just doing a bit of re-writing of some lessons which got me thinking that any atom could be used in theory, ie couldn't an atomic mass unit be defined as 1/14th the mass of a nitrogen-14 atom, or 1/24th the mass of a magnesium-24 atom?
    Why carbon-12?!
     
  2. Can anyone tell me why carbon-12 is used as the standard to which the mass of all other atoms are compared?
    I'm just doing a bit of re-writing of some lessons which got me thinking that any atom could be used in theory, ie couldn't an atomic mass unit be defined as 1/14th the mass of a nitrogen-14 atom, or 1/24th the mass of a magnesium-24 atom?
    Why carbon-12?!
     
  3. blazer

    blazer Star commenter

  4. Ssn77

    Ssn77 New commenter

    Initially 1H and then 16O were used because it was easier to get data for gases (Avogadro's law). Then there were discrepancies between measurements from bulk gases containing a mixture of isotopes, and spectroscopy measurements from single atoms. So it was decided to switch to a 12C standard to set a single new standard. Both C and O have the advantage of combining with many other elements.
     
  5. phlogiston

    phlogiston Star commenter

    Oxygen 16 used after H as oxygen combines with more elements than hydrogen.
    I understood that carbon 12 was chosen once mass spectrometers became the main way of measuring atomic mass. I read this in a book by Isaac Asimov a long tme ago, so this story may be revised from more accurate data.
    P
     
  6. Many thanks all!
     

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