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Dalton's Atomic Theory

Matter consists of indivisible particles called atoms.

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What's the Real Story?

What's the Real Story?


Credit: MIKI Yoshihito
Source: http://www.flickr.com/photos/mujitra/2559450199/
License: CC BY-NC 3.0

Space aliens have always been a great subject of debate. This conversation gets very heated sometimes, but never is resolved for a very simple reason – nobody has ever seen a space alien. So all we can do is discuss and debate. We cannot present any data about space aliens because there is no data to present.

Why It Matters

  • The ancient Greek philosopher Democritus thought about the world around him. He spent a lot of time debating with other philosophers trying to understand what matter was composed of. Lacking any way to test his ideas experimentally, he still came up with a good first approximation of the atom and chemical bonds. However, winning the debate did not prove his ideas were correct.
  • John Dalton also had some ideas about the atom. Dalton had an advantage over Democritus – he had some experimental data to back up his ideas. So Dalton could present his thinking with “here is what I believe to be true and here are the experiments that support my theory”. But he did not have the complete picture either.
  • Credit: Wikimedia
    Source: http://en.wikipedia.org/wiki/File:Daltons_symbols.gif
    License: CC BY-NC 3.0

    These drawings represent what John Dalton imagined atoms and molecules to look like [Figure2]

  • Dalton laid the groundwork for all further study of chemistry (which is why students learn about Dalton’s atomic theory). However, Dalton did not know about electrons and neutrons (other major constituents of the atom). He had no clue about the strange and confusing world of quantum theory with electrons moving in strange patterns. All this and more was still to come.
  • Watch a video at the link below to learn more about seeing atoms: https://www.youtube.com/watch?v=yqLlgIaz1L0

Show What You Know

Use the links below to learn more about Democritus and John Dalton. Then answer the following questions.

  1. According to Democritus, which atoms are smooth and slippery?
  2. What did Democritus say was between atoms?
  3. What job did John Dalton hold at age twelve?
  4. What question did Dalton first ask that led him to study atoms?
  5. What hypothesis did Dalton develop about the sizes of gases?

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    Image Attributions

    1. [1]^ Credit: MIKI Yoshihito; Source: http://www.flickr.com/photos/mujitra/2559450199/; License: CC BY-NC 3.0
    2. [2]^ Credit: Wikimedia; Source: http://en.wikipedia.org/wiki/File:Daltons_symbols.gif; License: CC BY-NC 3.0

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