Atomic Theory Timeline

  • Atomic Theory Timeline

    Before we get started on the Timeline thingy, there is a wee bit of background that we need to make sure gets introduced.

    Waaaay back, between 460BC-370BC, there was a philosopher named Democritus, who believed that all matter was made up of teeny, tiny solid particles that could not be seen or divided up. He gave those particles the name atoms, which actually means, indivisible.

    Not too many people were impressed with his idea, so it sat dormant for almost 200 years!



    Then came John Dalton. He lived from 1766-1844. He was fascinated with weather patterns and atmospheric gases and kept track with a log of the weather for over 50 years. His studies lead him to ask questions about what made up gases and other states of matter. His investigations lead him to 5 important statements about the particles that Democritus named atoms.

    ***Click HERE to see what those 5 statements are. Please copy them onto your timeline.

    Dalton didn't have too fancy of an idea of what atoms might actually look like. So this point in time, everyone just thought that they were solid spheres, kinda like a billiard 8-ball. 

    ***Please draw a "ball" like figure in John Dalton's space on the timeline. Make sure to color it in to represent its solid state.



    Our next scientist to study is J.J. Thomson. He lived from 1856-1940. He was very interested in how cathode-ray tubes (CRT) worked. CRTs are more commonly found today in the old boxy computer monitors and televisions. With his experiments he discovered the ELECTRON! (Write this down on your timeline)

    ***Click HERE (scroll down to your find the right guy) to read what his 2 major conclusions were. Please copy them onto your timeline.

    ***Click HERE where you'll also see a drawing of what Thomson thought the atom looked like. Draw this in the Thomson space, making sure that you color it in. 



    Ernest Rutherford took the ideas of J.J. Thomson and refined them even more. Rutherford lived from 1871-1937. His experiments involved shooting alpha particles through a piece of gold foil and then seeing where they ended up. Look HERE for images of the experiment.

    ***His experiments lead him to one very important conclusion. Click HERE (and then scroll down) to read what it was and copy it onto your timeline.

    ***Because of this new information, a new atomic model was created. Click HERE to see it and then draw & color it on your timeline. 
    Niels Bohr (pronounced "bore") actually worked with Rutherford in the same laboratory. With Rutherford's work to build upon, Bohr was able to present 4 principle ideas and design an even more accurate version of the atom with his investigations.

    ***Click HERE to see what those four principles are. Please copy down only the first 2 principles onto the timeline. 

    ***Bohr's atomic model is often referred to as the "planetary model". Click HERE to find out why. Make sure to include this illustration on your timeline. 





    Finally! We have come to what we know today about the Atomic Model!

    ***Please record these key points onto your timeline:
    1. Electrons do not "orbit" the nucleus, meaning the electrons do not follow a certain path as they buzz around the nucleus.
    2. Electrons can change levels.
    3. Each level (except for level 1) is made up of sub-levels. 

    ***If you look up images for the "quantum mechanical model" you will find lots of variations. But to keep things kind of simple, use this one to draw. Just remember that the electrons are moving so fast that they leave an energy trail behind them. Also...they are moving so fast that you can't really say where they might be at any given time.

    Congratulations! You're finished! Thanks for giving me your best effort!!!


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