• Question: How meany atoms make a pencil

    Asked by 454eura39 to Philip on 11 Nov 2014.
    • Photo: Philip Ratcliffe

      Philip Ratcliffe answered on 11 Nov 2014:

      Well a simple way to estimate this is to remember that Avogadroìs number (about 6 x 10^23 or 6 followed by 23 zeros – a very big number) is defined to be the number of carbon-12 atoms in 12 grams of carbon-12. Wood is pretty much made of of carbon (some hydrogen and oxygen to but one’s a bit heavier the other lighter so on average it’s about the same) so a pencil weighing about 12 grams has (very) roughly 6 x 10^23 atoms.

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