The outer most shell in an atom is the valence band. It has the shared electrons. They interact with the rest of the atoms and energy exchanges.
http://en.wikipedia.org/wiki/Band_Gap
Yes, they did the song, The Weight. The documentary "The Last Waltz" is about their last show together.
The electronic energy band of a http://www.answers.com/topic/crystalline solid which is partially occupied by electrons.
No. They're a secular band with a "few good songs"