| Chem 107 |
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Fall 2009 |
| Lecture Notes: 13 October |
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First I want to do a brief historical and qualitative overview of the structure of the atom. This information is for your general understanding and to provide some underpinnings for future discussions. Refer to your in-class notes.
I want to talk about one key type of evidence about atomic structure (spectroscopy), and then look at how electrons are arranged in atoms using a low resolution (low level of detail) picture.
Let's look for a moment at the nature of light and what we call spectra.
Electromagnetic Radiation comprises the various types of forms of radiation which propagate through space not associated with mass. The visible spectrum encompasses a very narrow region of the overall electromagnetic spectrum as seen below and on figure 7.2 on p 276 of your text.
Electromagnetic radiation behaves in most circumstances as waves [Figure 7.1 p 276] and can thus be characterized as waves.
public domain image via Wikipedia Creative Commons
Atoms display line spectra as seen below for Potassium (complex) and the much simpler example of Hydrogen (compared to a continuous spectra):
Spectra like these were among the most important evidence for the inner structure of atoms. The discreet lines indicate that the electrons reside in "orbitals" of discreet energies, with the colored emission lines indicating the the differences in energies between the different levels (ladder model - steps analogous to energy levels, damage from a fall analogous to "color" of light). The "bluer" the light the more energy/packet or energy/photon, the 'redder" the light the less energy/photon.
These spectra were also important in developing modern pictures of the atom:
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© R A Paselk
Last modified 12 October 2009