Chapter 43547Q43.11The energy of the photon is given to the electron. The energy of a photon of visible light is sufficientto promote the electron from the lower-energy valence band to the higher-energy conduction band.This results in the additional electron in the conduction band and an additional hole—the energystate that the electron used to occupy—in the valence band.Q43.12Along with arsenic (As), any other element in group V, such as phosphorus (P), antimony (Sb), andbismuth (Bi), would make good donor atoms. Each has 5 valence electrons. Any element in group IIIwould make good acceptor atoms, such as boron (B), aluminum, (Al), gallium (Ga), and indium (In).They all have only 3 valence electrons.Q43.13The two assumptions in the free-electron theory are that the conduction electrons are not bound toany particular atom, and that the nuclei of the atoms are fixed in a lattice structure. In this model, itis the “soup” of free electrons that are conducted through metals. The energy band model is morecomprehensive than the free-electron theory. The energy band model includes an account of the
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