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Homework Help: Homework help for chemistry

  1. Feb 23, 2008 #1
    Now, I just want to make it clear that normally I wouldn't ask for straight out answers, and I'm not asking for straight out answers here... Just a point in the right direction, unless it is absolutly necessary to give away the answer in explaining the concept to me so that I understand. Basically I am doign a mini-lab on the spectra produced by various elements when their gas is excited by electricity. The questions that came with the lab (at least he ones that have stumped me) include:

    What do the different colours in the line spectra represent?
    How does the Bohr model of the atom explain the spectrum seen for that atom (for example, my hydrogen spectrum that I observed had 2 lines on the left side, a purple and blue, and then one red line on the far right) ?

    So those tw oquestions, although we are supposed to make this up from the top of our head, have stumped me, and personally, I'd like to understadn the concept behind both of these questions. Can anyone explain? Please and thank you.
  2. jcsd
  3. Feb 23, 2008 #2
    1) Electrons being excited from one energy level to another (E.g. n=1 to n=2) the excitation only happens at discreet frequencies
    2) The bohr model if you search/look up is where electrons go in orbital paths at discreet energy levels much like a preset solar system with only set orbits that are allowed for the consituant planets. Therefore the electron in your hydrogen spectrum can only excite into certain discreet orbits, the transition from one orbit to the other requires electromagnetic radiation which has the energy, hv, necessary to go from one orbit to another (This is explained better by quantum theory, but bohr model is a much simpler view of it)
  4. Feb 23, 2008 #3


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  5. Feb 24, 2008 #4
    Ok, I understadn the first part... When electrons move between shells, they give off differing amounts of energy which correspond to differnt frequencies/wavelengths of the spectrum---> Differnt colours produced.

    But number 2 still stumps me. Sorry: I unerstand what the Bohr model is, but I think I need a slightly dumbed down explanation for the rest of this.
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