poodle + +cocker spaniel = = = = + +s orbitalp orbital cockapoo sp orbital

Poodle

+

+Cocker Spaniel

=

=

=

=

+

+s orbital p orbital

Cockapoo

sp orbital

The mixing of two or more atomic orbitals of similar energies on the same atom to produce new orbitals of equal energies

Called HYBRID ORBITALSAll have equal energyUsed for bonding with other atoms5 types of hybridization: sp, sp2, sp3,

dsp3,d2sp3

We have studied electron configuration notation and the sharing of electrons in the formation of covalentbonds.

Methane is a simple natural gas. Its molecule has a carbon atom at the center with four hydrogen atoms covalently bonded around it.

Lets look at a molecule of methane, CH4.

What is the expected orbital notation of carbon in its ground state?

(Hint: How many unpaired electrons does this carbon atom have available for bonding?)

Can you see a problem with this?

You should conclude that carbon You should conclude that carbon only has only has TWOTWO electrons available for electrons available for bonding. That is not enough.bonding. That is not enough.

What is taking place in order that What is taking place in order that carbon may form four bonds?carbon may form four bonds?

The first thought The first thought that chemists had that chemists had was that carbon was that carbon promotes one of its promotes one of its 2s2s electrons… electrons………to the empty to the empty 2p2p orbital.orbital.

However, they quickly recognized a problem with such an arrangement…

Three of the carbon-hydrogen bonds would involvean electron pair in which the carbon electron was a 2p, matched with the lone 1s electron from a hydrogen atom.

This would mean that three of the bonds in a methanemolecule would be identical, because they would involveelectron pairs of equal energy.But what about

the fourth bond…?

The fourth bond is between a 2s electron from the carbon and the lone 1s hydrogen electron.

Such a bond would have slightly less energy than the other bonds in a methane molecule.

This bond would be slightly different in character thanthe other three bonds in methane.

This difference would be measurable to a chemistby determining the bond length and bond energy.

But is this what they observe?

The simple answer is, “No”.

Chemists have proposed an explanation – they call it Hybridization.

Measurements show that all four bonds in methane are equal. Thus, we need a new explanation for the bonding in methane.

In the case of methane, they call the hybridization sp3, meaning that an s orbital is combined with threep orbitals to create four equal hybrid orbitals.

These new orbitals have slightly MORE energy thanthe 2s orbital…

… and slightly LESS energy than the 2p orbitals.

1s2sp3 2sp3 2sp3 2sp3

Here is another way to look at the sp3 hybridization and energy profile…

Other types of hybridization that atoms undergo:

These include spsp hybridization, in which one s orbital combines with a single p orbital.

This produces two hybrid orbitals, while leaving two normal p orbitals

Another hybrid is the spsp22, which combines two orbitals from a p sublevel with one orbital from an s sublevel.

One p orbital remains unchanged.

Beginning with elements in the third row, “d” orbitals may also hybridize

dsp3 = five hybrid orbitals of equal energy

d 2sp3 = six hybrid orbitals of equal energy

FormsForms Electron geometryElectron geometryHybridizatioHybridizatio

n of “A”n of “A”

AX2 Linear sp

AX3, AX2E Trigonal Planar sp2

AX4, AX3E, AX2E2 Tetrahedral sp3

AX5, AX4E, AX3E2, AX2E3 Trigonal bipyramidal

dsp3

AX6, AX5E, AX4E2 Octahedral d2sp3

A = central atomA = central atom

X =X = atoms bonded to Aatoms bonded to A

E = nonbonding electron pairs on AE = nonbonding electron pairs on A

• Does not apply to isolated atoms- a theoretical model to explain covalent bonding

• Has a different shape than pure orbitals

• Number of hybrid orbitals is equal to the number of pure orbitals involved in hybridization

• Bonds are formed by an overlap of hybrid-hybrid orbitals or hybrid-pure orbitals

1. Draw the Lewis structure2. Predict the overall arrangement of

the electron pairs (bonding and nonbonding) using VSEPR

3. Deduce the hybridization by matching the arrangement of electron pairs with those of the hybrid orbitals

Determine the hybridization of the central atom in the following molecules: (a)BeH2, (b) AlI3 and (d) PF3

Determine the hybridization of the central atom in the following molecules: (a)BeH2, (b) AlI3 and (d) PF3

Determine the hybridization of the central atom in the following molecules: (a)BeH2, (b) AlI3 and (d) PF3

Describe the hybridization of phosphorus in PBr5

Describe the hybridization of carbon in CH2O

Single bond 1 sigma bond

Double Bond 1 sigma, 1 pi bond

Triple Bond 1 sigma, 2 pi bonds

Sigma () bonds exist in the region directly between two bonded atoms.

Pi () bonds exist in the region above and below a line drawn between two bonded atoms.

C C

H

H

H

H

H

H

Ethane

1 bond

CC

H

H

H

H

C C

H

H

H

H

Ethene

1 bond

1 bond

C C HH

CC HH

Ethyne

1 bond

1 bond

1 bond

H

H

H

H

H

H

H

H

H

H

H

H

Pi bonds () contribute to the delocalized model of electrons in bonding, and help explain resonance

Electron density from bonds can be distributed symmetrically all around the ring, above and below the plane.