What is the hybridization in #"CO"_2#?

You must first draw the Lewis structure for #"CO"_2#.

According to VSEPR theory, we can use the steric number #("SN")# to determine the hybridization of an atom.

#"SN"# = number of lone pairs + number of atoms directly attached to the atom.

• #"SN = 2"# corresponds to #sp# hybridization.
• #"SN"= 3"# corresponds to #sp^2# hybridization.

We see that the #"C"# atom has #"SN = 2"#. It has no lone pairs, but it is attached to two other atoms.

It has #sp#hybridization.

Each #"O"# atom has #"SN = 3"#. It has 2 lone pairs and is attached to 1 #"C"# atom.

Just as the carbon atom hybridized to form the best bonds, so do the oxygen atoms.

The valence electron configuration of #"O"# is #["He"] 2s^2 2p^4#.

To accommodate the two lone pairs and the bonding pair, it will also form three equivalent #sp^2# hybrid orbitals.

Two of the #sp^2# orbitals contain lone pairs, while the remaining #sp^2# orbital and the unhybridized #p# orbital have one electron each.

We can see this arrangement in the #"C=O"# bond of formaldehyde, which is equivalent to the right-hand side of the #"O=C=O"# molecule.

(from www.slideshare.net)

There is a similar arrangement on the left side of the #"O=C=O"# molecule, but the #pi# bond is horizontal rather than vertical.

Here is a video about the hybridization of carbon dioxide.