Lyndons Worksheet Question 2

[Vincent Leong 2B]

For the composition of each bond and hybridization of each lone pair of HCOOH, how do we know to include the energy level when writing the hybridization? For example, in the C-O bond, the notation is sigma(C2sp^2, Osp^3). Why does oxygen not have a 2 before its sp3 hybridization? Also, how can we tell if an atom will occupy an unhybridized p orbital instead of a hyrbidized sp^2 orbital (Im talking about the double bonded O in HCOOH)?

[Victoria Li 1L]

You're right actually! It should be O2sp², my bad. And for the double bonded O: iirc it wants to make sigma bonds first, so its stabler hybrid orbitals are used in making the sigma bond. The pi bond is then formed with the leftover unhybridized 2p orbital. This happens because the electron wants to stay in a different orbital to reduce spin pair repulsion.