# enmaexam1 - Quantum Numbers n – Principal Quantum number...

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Unformatted text preview: Quantum Numbers n – Principal Quantum number - size l – n -1 (angular) - shape mp - -l to l (magnetic) - orientation ms - +1/2 or -1/2 (spin) Pauli Exclusion principle: For an individual atom, at most two electrons, which necessarily have opposite spins, can occupy the same state. X’s are the electronegativies. % ionic character= (1-exp(-(0.25)(X A-X B ) 2 ))x100 Where X A > X B Covalently bonded substances have low MP due to weak intermolecular bonds (Van der waals) FCC Coordination number 12 (n=4atoms/cell) = a 2R2 , apf =.74 BCC coordination number 8 (n=2 atoms/cell) =( )/ a 4R 3 , apf =.68 Simple cubic coordination number 6 = a 2R = APF volume atomsvolume unit cell APF = Vs/Vc Vs = n*4/3*pi*R 3 Vc = a 3 HCP (n =6 atoms per cell) = = V c332a2 wHere a 2r Density = ρ nAwVcNa (g/cm 3 ) = ( + ) ρ n' Ac AA VcNa Sum of Cations + Sum of Anions Atomic weights N a =6.022*10 23 atoms/mol A w =atomic weight =# Linear Density of atoms centered on the vectorlength of direction vector Linear Density = # atoms / length (g/cm) BCCld110 = 2 atoms BCCld111 = 2 atoms distance 4R FCC110 = 2 atoms FCC100 = 1 atom FCC110 = 3 atoms FCC111 = 2 atoms Planar Density = # atoms/ area (g/cm 2 ) BCC100 = 1 atom BCC110 = 2 atoms BCC111= 1 atom; formula = 3*1R 2 /16sqrt(3) FCC111 = 2 atom; formula = 1/2R 2 sqrt(3) The larger the ion, the larger the coordination number Coordination number Cation anion radius ratio 2 <.155 3 .155-.225 4 .225-.414 6 .414-.732 8 .732-1.0 Structur e Name Structur e type Anion packin g Catio n # Anio n# Exampl es Rock salt AX FCC 6 6 NaCl, MgO, FeO CsCl AX Simpl e cublic 8 8 CsCl Zinc Blende AX FCC 4 4 ZnS, SiC Fluorite AX 2 Simpl e cubic 8 4 CaF 2 (Ca is in every other cube Perovski te ABX 3 FCC 12(A ) 6(B) 6 BaTiO 3 Spinel AB 2 X 4 FCC 4(A) 6(B) 4 MgAl 2 O 4 Rock salt = + a 2rcat 2ran Seven crystal systems <111> family of directions {111} family of planes...
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## This note was uploaded on 08/02/2011 for the course ENMA 300 taught by Professor Alsheikhly during the Spring '11 term at University of Maryland Baltimore.

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