Hybridization of Atomic Orbitals Some Material Copyright PGCC CHM 101 Sinex Some Graphics from Nelson Chemistry 12 Textbook

Atomic Orbitals Don’t Work? To explain molecular geometry: In methane, CH 4, the shape is tetrahedral. The valence electrons of carbon should be two in s, and two in p. The p orbitals would have to be at right angles. The atomic orbitals change when making a molecule

Valence Bond Theory Atomic orbitals overlap when a bond is formed between atoms A new set of orbitals is formed Each orbital contains a pair of electrons These are called hybrid orbitals How do they look? See p234 Table 1

Hybridization p234 Table 1 Ex: sp 3 hybridization

sp 3 Hybridization The s and p orbitals blend and end up with the tetrahedral geometry. one s orbital combines with three p orbitals. sp 3 hybridization has tetrahedral geometry.

2p Hybridizationsp 3 2s Energy In Terms of Energy

Notation? sp 3 One s orbital and three p orbitals Each orbital holds 2 electrons

Illustrating Hybridization Animation of hybridization hybridization Visualization of orbitals hybrid orbitals

Double and Triple Bonds Ex: C 2 H 4 Double bond acts as one pair. Geometry - trigonal planar Have to end up with three blended orbitals. Use one s and two p orbitals to make sp 2 orbitals. Leaves one p orbital perpendicular.

Where is the P orbital? Perpendicular The overlap of orbitals (end-to-end) makes a sigma bond (  bond)

hybrid orbitals – sp, sp 2, or sp 3

formation of  bond

remaining p orbitals form sp or sp 2  bond

The overlap of orbitals (side-to-side) makes a pi bond (  bond) Planar molecule (each carbon is trigonal planar) with  cloud above and below the plane  bond hinders rotation about the carbon-to- carbon bond

sp Hybridization End up with two lobes 180º apart. p orbitals are at right angles Makes room for two  bonds and two  bonds. A triple bond or two double bonds.

Bond Formation From Hybridization Single bond - sigma bond Double bond – sigma bond + pi bond Triple bond – sigma bond + pi bond + pi bond How are the two pi bonds in the triple bond oriented? end-to-end side-to-side

How about the electron density around a C-C bond? C2H6C2H6 C2H4C2H4 C2H2C2H2 single bonddouble bondtriple bond Polar or Non-polar H + attack?

Summary