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Molecular Geometry and Polarization. Shapes of Molecules. Valence Shell Electron Pair Repulsion Theory (VSEPR) a. Bonded electrons b. Lone Pairs. 1. Linear (180 o ) BeH 2 CO 2. 2. Trigonal Planar (120 o ) NO 3 -. 3. Tetrahedral (109.5 o ) CH 4.
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Shapes of Molecules Valence Shell Electron Pair Repulsion Theory (VSEPR) a. Bonded electrons b. Lone Pairs
1. Linear (180o) BeH2 CO2
O H H
Shapes of Molecules Ex: Multiple Bonds: N2 H2CO HCN SO2
SO22+ SO22- SO2 SO3 SF3- PF4- XeCl5+ BrF4-
Predict the molecular geometry of: SnCl3- O3 SeCl2 CO32- SF4 IF5 ClF3 ICl4-
WarmUp • ClF4- SiCl3- SO2 • SCl4 SeO3 BrCl5 BrCl3
Polar Molecules 1. Polar molecule – Overall, the electrons are attracted more to one end of an entire molecule 2. Non-Polar Molecule – The electrons are spread out evenly over the entire molecule -/ + Partial (not full) charges
Examples: H2 H2O CH4 H2CO
Electron Density H2 H2O CH4 H2CO
Polar Molecules BeCl2 NH3 CO2 SO2 SF6 BCl3 CH2Cl2
SCO CH3F BH2Cl PH3
CHF3 CH2F2 SO3 SO32- NF3 CH3CHO
Hybrid Orbitals • A mixing of the atomic orbitals (s, p, d, f) of the central atom • Electrons no longer move in the old orbitals, but in a new pattern
BeF2 Isolated Be 1s22s2 (Note that all Be: electrons are paired) To bond Be must unpair some electrons: Bonded Be 1s22s12p1 •Be•
Be is called an “sp” hybrid. • Drawings: Isolated BeBeF2
CH4 Isolated C 1s22s22p2 Bonded C 1s22s12p3
Isolated C Bonded C sp3
Effect of Lone Pairs • Lone pairs do count towards hybridization • Ex: H2O
Examples CCl4 NH3 PF5 SF6 XeF4 BrF3
PH3 H2S SF5- SF4 CO32- HCN BrCl3 CH4
H2S SO2 SO22- AsCl5 ClF3 KrF4
Hybrid Orbitals and Multiple Bonds • sigma () bonds – single bonds formed by hybrid orbitals • pi () bonds – double or triple bonds, not formed by hybrid orbitals H H H – H C=C :N=N: H H One bond One bond plus One bond plus one bond two bonds
Consider C2H4 • Each C is sp2 • Double bond does not count toward hybridization