What is the orbital hybridization of iron in heme?

Answer 1

Hybridisation theory does not work for transition metals. Linus Pauling thought it did, but he was wrong.

If you don't believe me, look at an advanced textbook such as Cotton and Wilkinson, and you will see that you have to use something called ligand field theory, which is a kind of molecular orbital theory.

If you are asking this question yourself, it is a very interesting question to raise, and I think it is interesting that it does not have a straight answer. If you have been asked this question as an assignment, I would very much like to know where it came from, as it might mislead students less intelligent than you.