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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. Xs 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 = nAwVcNa (g/cm 3 ) = ( + ) 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 Chapter 4 (Polymers) Avg Molecular Weight - Mn = x * i Mi-Mw = w * i Mi Mi = Mean mol weight xi fraction of the total number chains wi weight avg = DP Mnm where m is average mol weight of repeat unit i.e CH4 m = (1*12g/mol + 4*1g/mol) % = (- ) (- ) crys c s a s c a C is crystalline, a is totally amorphous, and s is density tbd Three dimensional networks also possible in highly crosslinked materials Chapter 5 =- Nv Nexp QvkT k= -1.38x10-23 J/atom*k = 8.62x10-5 ev/atom*k = N NAAw Schottky/Frenkel =- ; = + ; = Nv Nexp QvkT ave 100C11 C22 Aave + 100C1A1 C2A2 C 1 is wt% C 1 = m1/(m1+m2) =- ( ) Nm 2n 1 100M 2 Shear stress to move dislocation =- Ce Kdb = shear stress required to move a dislocation C and K = material constants....
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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.
- Spring '11