The main objective in today's lecture was to compare and contrast the differences we observe between a molecule and a solid. In molecules we have isolated units giving rise to discreet energy levels we observe in a molecular orbital diagram. In a solid the infinite number of atoms present leads to bands of molecule orbitals, which are wider in energy than the molecular orbitals in molecules.
Many of the physical properties of solids are dictated by the energy gap of the highest energy band containing electrons, which is referred to as the valence band, and the lowest energy band that does not contain electrons, or the conduction band.
The magnitude of the difference in energy between these two bands is referred to the band gap. Band gaps are typically reported in units of electron Volts (eV), so be sure to know how to convert from eV to Joules and vice versa.
At the end of class I briefly discussed photovoltaic devices and what chemists can do to manipulate the band gap and design better materials with more desirable properties. We will pick up with that discussion on Monday. If you want to get a better glimpse of photovoltaic devices and solar cells, here is a neat link.
Inspirational Quote of the Day:
"The time to prepare isn’t after you have been given the opportunity. It’s long before that opportunity arises. Once the opportunity arises, it’s too late to prepare."
Song Played Before Class:
Rascal Flatts - Here's To You
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