I'm working a problem with the BH3 molecule. Therefore boron is 1s^2 2s^2 2p^1, and using the hypotetical method, it forms hybird sp2 orbitals. Promoting an electron to get 1s^2 2s^1 2p^2. My question is that, it will form 3 bonding orbitals, one from the 1s and 2 from the 2p orbitals... what happends to the third 2p orbital? If I do an energy level diagram, do I have to list this orbital as a nonbonding one?