electronic+structure

Here are links for a review of electron addresses and electron configurations.

Since the focus for organic chemistry is carbon, we will primarily use it to model hybridization.

Here is the 'normal' electron orbital notation for carbon:

Based solely on the fact that its configuration has two unpaired electrons, like oxygen, one would be led to think that carbon can form two bonds. However, we know that carbon forms four bonds (from the fact that methane's structure is CH4).

So, how does carbon form four bonding sites? It does so by //hybridizing// its valence shell. The 2s and the three 2p orbitals 'blend' together to form four hybrid orbitals, called sp3 hybridized orbitals.

Now, carbon has four bonding sites!



But what about a compound like formaldehyde (CH2O), where carbon only has three atoms bonded to itself?

Recall the Lewis diagram for formaldehyde:

This compound contains a double bond, which of course still follows the four-bond principle for carbon. But this carbon has a distinct hybridization. In this carbon, one of the 2p orbitals is left alone; only three new hybridized orbitals forms (called sp2 orbitals):



The third and final state of hybridization for carbon is the sp orbital. This occurs when carbon undergoes triple bonding, such as in acetylene (C2H2).



Here is the orbital notation description of the sp hybridized orbital. Note there are two unused 2p orbitals:





Watch this [|flash player presentation] for a visual on hybridization.

Here is a 3D model of each hybridization.

Try these animated models.


 * LCAO-MO**

When atomic orbitals (such as a 2s and a 2p orbital) combine, or hybridize, they undergo what is called linear combination of atomic orbitals (LCAO).

This is simply the mathematical addition of the orbitals' wave functions (like math functions), with the sum being the hybrid orbital, as discussed in the section above.

Here is a diagram of three different hybridizations, and the associated bond types, for ethane, ethene, and ethyne:

Hybridization of CO 2 :