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Types of Hybridization and Hybrid Orbitals

SECTION 9 - Covalent Bonding and Molecular Orbitals

sp2 hybridization

➞ Often used with double bonds or triple bonds.

ex:  C2H4 , with 12 valence electrons:

sp2 Hybridization

In the drawing above, we see that each carbon is surrounded by 3 effective pairsAs before, an isolated carbon is 1s22s22p6 and 2s and 2p are the valence atomic orbitals.

We need hybrid orbitals.

➞ sp3-orbitals won't work because they're tetrahedral (4 effective pairs) with 109.5° bond angles.

Here's how we can "hybridize" the one 2s and three 2p atomic orbitals into three sp2 hybrid orbitals...

sp2 Orbital Formation from Atomic Orbitals

The 3 sp2-orbitals (hybrid orbitals) are used to share electrons in an area centered on a "line" running between the atoms.  These are called sigma bonds (σ-bonds):

C2H4 Sigma and Pi Bonds

As you can see in the above image on the left, all 5 sigma bonds share an electron pair in a region directly between the 2 atoms.

The sigma bonds in our C2H4 example above are either 1s—sp2 or sp2—sp2.

What about the double bond?

  ➞ And what about the remaining "left over" 2p atomic orbital?

  ➞ Well... the second bond between the two carbon atoms (the double bond) results from sharing an electron-pair using the two 2p atomic orbitals that are perpendicular to the three sp2-orbitals on each carbon.

  ➞ Here's a visualization of all that:

Pi Bonding in C2H4

These parallel p-orbitals can share an electron-pair (↑↓), which occupies the space above and below a "line" joining the carbon atoms, to form a pi bond (π-bond).

  ➞ So in the ethylene molecule above (C2H4), there are:
          - 5 σ-bonds  (sigma bonds)
          - 1 π-bond  (pi bond)


sp hybridization

➞ Used when an atom in a molecule has only 2 effective pairs around it. In the example below, the carbon (C) becomes sp-hybridized...

ex:  CO2 , with 16 valence electrons:

Formation of sp Hybrid Orbitals

NOTE - Both oxygens in O=C=O are sp2-hybridized because they each have 3 effective pairs around them ➞ 1 carbon, + 2 sets of lone pairs = 3 pairs.

Here's how that looks...

sp and sp2 Orbitals in CO2

The two 2p-orbitals on carbon are perpendicular to each other.  Additionally, each of the C=O double bonds consist of one sigma bond and one pi-bond.


dsp3 hybridization

➞ Used when the atom requires 5 effective pairs around it in a molecule.

ex:  PCl5 , with 40 valence electrons:

dsp3 Hybridization

Phosphorus' 5 dsp3-orbitals are formed from one d-orbital, one s-orbital, and three p-orbitals. They're all equivalent and are used to make 5 identical bonds to the chlorine atoms.

** a set of 5 effective pairs around an atom (i.e. Phosphorus, P) requires a trigonal bipyramidal arrangement and dsp3 hybridization.


d2sp3 hybridization

➞ Used when the atom requires 6 effective pairs around it in a molecule.

ex:  SF6 , with 48 valence electrons:

d2sp3 Hybridization

Sulfur's 6 d2sp3-orbitals are formed from two d-orbitals, one s-orbital, and three p-orbitals. They're all equivalent and are used to make 6 identical bonds to the fluorine atoms.

** a set of 6 effective pairs around an atom (i.e. Sulfur, S) requires an octahedral arrangement and d2sp3 hybridization.


In my next video blog post covering SECTION 9 - Covalent Bonding and Molecular Orbitals,

We'll practice doing a bunch of Hybridization Examples and Practice Problems...