Exam 2 � Review Sheet

Exam 2 � Review Sheet - Exam 2 Review Sheet Metallic...

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Exam 2 – Review Sheet Metallic Crystals Dependence of electrical conductivity with T: E.C. of a metal decreases with temperature and a semiconductor E.C. increases with temperature. Primitive unit cell – CN= , # atoms=8, lattice point=(1/8 *8) Face-centered unit cell – CN=12, # atoms=14, lattice point=(1/8*8+1/6*6) Body-centered unit cell – CN=8, # atoms=9, lattice point=(1/8*8 + 1) CCP = fcc ; CN, # atoms HCP Review calculations of metallic radius from density for fcc and bcc unit cells: The metallic radius is half of the distance between the nearest neighbor atoms in a solid state metal lattice, and is dependent upon coordination number.? Semiconductors Dependence of electrical conductivity with T: E.C. of a metal decreases with temperature and a semiconductor E.C. increases with temperature. Trends in BG energy for Group 4 and 3,5-semiconductors: Down a group the BG decreases. Larger the atoms the smaller the BG. Smaller particle size is greater BG. In 3 doped( p type) semiconductors a small acceptor band is located close to the valance band leaving positive holes. In 5 a small donor band is populated close to the conduction band (n type). N for negative and p for positive. Procedure for determining band gap energy from the temperature dependence of conductivity: ? Lattice structure of Group 4 and 3,5-semiconductors:? Ionic Compounds Periodic trends in ionic radii: group 1,2,17 increase when going down rows. D-block metals have very similar ionic radii and when they decrease in charge their ionic radii increase.
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Exam 2 � Review Sheet - Exam 2 Review Sheet Metallic...

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