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How do we know that matter consist of atom?

  1. Jul 15, 2010 #1
    1. The problem statement, all variables and given/known data

    How do we know that matter consist of atom?

    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Jul 15, 2010 #2

    alxm

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    The number of atoms or molecules in a given amount of substance is related by Avogadro's Number. What ways exist of determining it?
     
  4. Jul 22, 2010 #3
    If I remember correctly, it was John Dalton who first proposed the existence of atoms. Read up on how he came to that conclusion. The word 'valency' comes into it.
     
  5. Jul 23, 2010 #4

    alxm

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    (Well, if you discount the Greeks..) But valency doesn't come into Dalton's rationale, actually. (It wasn't a known concept during his lifetime, even.) Dalton had found the "law of fixed proportions"; that chemical elements appeared to react and combine in certain fixed proportions, which the atomic hypothesis explained.

    But it wasn't until the Karlsruhe congress of 1860 that the hypothesis was generally accepted among chemists, (but not among contemporary physicists, notably Ernst Mach). It wasn't until Jean Perrin's 1913 book "Les Atomes" that the last die-hards were convinced.
     
  6. Jul 23, 2010 #5
    He didn't use the word, granted. I was merely laying a crumb trail for the OP to follow.
     
  7. Jul 23, 2010 #6
    Or look up STM images on google :)
     
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