CHEM 121 Lecture Notes - Sigma Bond, Lewis Structure
42 views2 pages
November 17th, 2011
November-17-11
8:00 AM
Valence Bond Theory
Orbitals merge together
Sigma Bond ("End on Bonding")
Overlap of orbitals along internuclear axis
Internuclear axis = line going through both atoms' nuclei
Bonds form only with orbitals of same phase
Pi Bond ("Side on Bonding")
Phase of one orbital matches other on same side of nodal plane and same
holds true for other bond
Internuclear axis within nodal plane
Will always have a sigma bond
<--->
Single bonds = sigma bonds, pi bonds = multiple bonds - 1
Hybridization
Mixing of orbitals to form new orbitals
Common: sp, sp2, sp3, sp3d, sp3d2
"offspring" of "parent" orbitals
Schemes
sp Orbitals
Two sp orbitals created; both oriented 180o from each other
2 in, 2 out
sp2 Orbitals
Three orbitals are created; oriented 120o from each other
3 in, 3 out
sp3 Orbitals
Four orbitals are created
4 in, 4 out
Creates tetrahedral formation
Application of VBT to Hybridized Atomized Molecules
1. Draw Lewis structure of molecule
1. Determine parent shape
2. Match shape to scheme:
Parent Shape Bond
Angles
Hybridization of
Central Atom
Linear 180osp
Trigonal Planar 120osp2
Tetrahedral 109.5osp3