Eng 45 - Chapter 1 - Structure(22)

Eng 45 - Chapter 1 - Structure(22) - Materials Scien ce...

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Materials Science Fall, 2007 Page 21 Metallic bonding The second category of shared electron bonds is called metallic. Metallic bonds are unsaturated; only some of the available valence states are needed when all valence electrons are shared. A classic example of the metallic bond is the body-centered cubic (BCC) modification of solid sodium (Na). In BCC sodium each atom has a single va- lence electron, and each atom has eight neighbors. When the valence electrons are fully shared with neighboring atoms many available valence states are left empty. The bonds are unsaturated, and hence metallic. The transition metals have additional empty d-states in the ion core, and can achieve additional bonding through the partial sharing of these. = ion core sea of = valence electrons Fig. 2.4: Illustration of metallic bonding. Valence electrons bind a distri- bution of ion cores. Since the number of valence electrons in a metallic solid is much less than the number of available bonding states, it is somewhat meaningless to associate a particular
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This note was uploaded on 01/26/2010 for the course ENGLISH 45 taught by Professor Morris during the Spring '10 term at University of California, Berkeley.

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Eng 45 - Chapter 1 - Structure(22) - Materials Scien ce...

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