Hybridization ofAtomic Orbitals

Some Material Copyright PGCC CHM 101 SinexSome Graphics from Nelson Chemistry 12

Textbook

Atomic Orbitals Don’t Work?

To explain molecular geometry:

• In methane, CH4 , 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 1Ex: sp3 hybridization

sp3 Hybridization

• The s and p orbitals blend and end up with the tetrahedral geometry.

• one s orbital combines with three p orbitals.

• sp3 hybridization has tetrahedral geometry.

2p

Hybridization sp3

2s

Energy

In Terms of Energy

Notation?

sp3

•One s orbital and three p orbitals•Each orbital holds 2 electrons

Illustrating Hybridization

Animation of hybridizationhybridization

Visualization of orbitalshybrid orbitals

Double and Triple Bonds

Ex: C2H4

• 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

sp2 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, sp2, or sp3

formation of bond

remaining p orbitals form sp or sp2

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?

C2H6

C2H4C2H2

single bond double bond triple bond

Polar orNon-polar

H+

attack?

Summary