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 = (1exp((0.25)(X AX 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 .7321.0 Chapter 4 (Polymers) Avg Molecular Weight  Mn = x * i MiMw = 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 ρc ρs ρa ρs ρc ρa 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= 1.38x1023 J/atom*k = 8.62x105 ev/atom*k = N NAρAw Schottky/Frenkel = ; = + ; = Nv Nexp QvkT ρave 100C1ρ1 C2ρ2 Aave + 100C1A1 C2A2 C 1 is wt% C 1 = m1/(m1+m2) = ( ) Nm 2n 1 100M 2 Shear stress to move dislocation = τ Ce Kdb τ = shear stress required to move a dislocation C and K = material constants....
View
Full Document
 Spring '11
 AlSheikhly
 Chemistry, Materials Science, Atom, Ion, Pauli exclusion principle

Click to edit the document details