Hybridized Orbitals

V-B theory can’t explain some observations aboutmolecular compounds without the concept of hybridized orbitals.

i.e., covalent (NM/NM) compounds

In…

BeF2

(LS) …the central atomSHOULD be…

…but is ACTUALLYhybridized to be…

…the resultthen being…

2 hyb. sp orbs.2 unhyb. 2p orbs.2s 2p

BF33 hyb. sp2 orbs.1 unhyb. 2p orb.2s 2p

2psp

sp2 2p

CH4 4 hyb. sp3 orbs.2s 2p sp3

H2O 4 hyb. sp3 orbs.2s 2p sp3

PF53s 3p sp3d3d 3d

5 hyb. sp3d orbs.4 unhyb. 3d orbs.

XeF2sp3d5s 5p 5d 5d

5 hyb. sp3d orbs.4 unhyb. 5d orbs.

XeF4sp3d25s 5p 5d 5d

6 hyb. sp3d2 orbs.3 unhyb. 5d orbs.

: BeF :

::F

::

B :

::F

:F

::

:F:

:

CH HH

H

OHH

:

:

P :

::F

:F

::

:F:

:

:: :F

:

::F

: XeF :

::F

::

: ::

: XeF :

::F

::

::F: :

F::

::

KEY: EDG hybridization of central atom

linear sp

trig. planar sp2

tetrahedral sp3

trig. bipyr. sp3d

octahedral sp3d2

sp hybridization

sp hybridization occurs when one s and one of the three porbitals hybridize. It results in the creation of two sp hybridorbitals (orange). The other two p orbitals (purple) areunhybridized; they retain the “figure-8” or “dumbbell” shape.

Multiple Bonds

s (sigma) bonds are bonds in which the e– density isalong the internuclear axis.

-- These are the single bonds we have considered up to this point. -- e.g., s-s, s-p, or p-p overlap, and also p-sp hybrid overlap

Multiple bonds result from the overlap of two p orbitals(one from each atom) that are oriented perpendicularlyto the internuclear axis. These are p (pi) bonds.

sigma (s) = single

pi, multiple, unhybridized

NHH

H

..

The bondsin ammoniaare s bonds.

p bonds are generally weaker than s bonds becausep bonds have less overlap.

C C

H

H

H

H

For ethene (C2H4)…

C=C–––

– H

H

H

H

For each carbon atom, thereare 3 sp2 hybridizedorbitals; these form s

bonds (- - - -) with C or H.

Where unhybridizedorbitals overlap,

a p bond ( ) is formed.

Single bondsare s bonds.

Double bonds consist ofone s and one p.

Triple bonds consist ofone s and two p.

e.g., C2H2

e.g., C2H4

e.g., C2H6

Experiments indicate that allof C2H4’s atoms lie in thesame plane. This suggeststhat p bonds introducerigidity (i.e., a reluctance to rotate) into molecules.

-- p bonding does NOT occur with sp3 hybridization, only sp and sp2

-- p bonding is more prevalent with small molecules (e.g., C, N, O) (Big atoms don’t allow enough

p-orb. overlap for p bonds to form.)

resonance structures.

Delocalized p Bonding

Localized p bonds are between…

-- e.g., C2H2, C2H4, N2

Delocalized p bonds are“smeared out” andshared among…

-- These are common for molecules with…

-- The electrons involved in these bonds are delocalized electrons.

The nitrate ion (NO3–) has

delocalized electrons.

[ ]N=OO–....

....

..

..

....O

–

> two atoms.

two atoms only.

Consider benzene, C6H6. -- Each carbon atom is ___ hybridized.

-- This leaves... a 2porbital on each Cthat is oriented to plane of m’cule.

C

C

C

C

C C

H

H

H

H

H

H

-- 6 e– shared equally by 6 C atoms

sp2

Which of the following exhibit delocalized bonding?

H3C–C–CH3

O=

SO42–

SO2

sulfate ion

sulfur dioxide

18 e–

32 e–

O–S=O...... ..

....

“YEP.”

HH–C–C–C–H

O

=

.. ..

––

H

–

H

H

–

“NOPE.”

“NOPE.”[ ]S–OO–....

..

....

....

....

O

O

.. ....

2–

24 e–

propanone

(res.)