hybridization of atomic orbitals some material copyright pgcc chm 101 sinex some graphics from...

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