RDGLED - LEDs Revised: 5/04/05 LIGHT EMITTING DIODES Solids...

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LEDs Revised: 5/04/05 LIGHT EMITTING DIODES Solids are classified as metals, semi-metals, or non-metals by their ability to conduct heat and electricity. "Band theory" is a bonding model for solids that explains conductivity by assuming a higher energy level exists above the valence electron level called the "conduction band". The theory assumes electrons in the conduction band are not attached to individual atoms (localized) but move freely throughout the entire solid (delocalized). In a metal the delocalized electrons in the conduction band behave like a "sea of electrons" which "surges" throughout the solid, forming an electrical current. The band gap is the energy needed to promote an electron from the lower energy valence band into the higher energy conduction band (Figure 1). The band gap in metals is very small. Ordinary thermal energy (present at room temperature) promotes the valence electrons to the conduction band where they move freely about the metal. Therefore, metals are called "conductors" because they easily carry current.
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This note was uploaded on 11/21/2010 for the course CHEMISTRY Chem 1LE taught by Professor Dr.kimberlyedwards during the Spring '10 term at UC Irvine.

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RDGLED - LEDs Revised: 5/04/05 LIGHT EMITTING DIODES Solids...

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