I am a high school student and I am very confused in Molecular orbital theory, it says that when two orbitals overlaps in the same phase, they form antibonding orbitals and when they overlap in opposite phase forms antibonding orbital, but my questions are:

  1. how those orbital overlap in the same and opposite phases simultaneously, forming antibonding and bonding orbitals together?? or those are the electrons which are overlapping?

  2. if orbitals are the regions where there is probability to find the electron then how two vacant orbitals can overlap each other? for e.g if there is a 3 electron system then two will be in bonding and 1 will be in antibonding then if I think of it as electrons overlapping then is this electron overlaps with the vacant orbital to form antibonding orbital? do vacant orbitals really have self existence(isn't it just the empty space)? if they exist independently then why do we take there energies to be 0 if there is no electron in them?

  3. In crystal field theory, we say that d orbitals splits due to the repulsion faces from ligands, but even if they are empty we still split them how is this even possible? for e.g it is written that if there is say d1 configuration in octahedral complexes then the d orbitals located in path of ligand will face higher repulsion from the ligands so the energy levels are not degenerate anymore and but, isn't this statement very vague? if there is only 1 electron in the d orbitals then only that will face repulsion how can the empty space is facing repulsion?

there are several answers related to molecular orbital theory but I am looking for the one I can understand at my level as there are many difficulties to digest this.

  • $\begingroup$ @ArunBharadwaj I think (probably) the first and second points have already been covered on the site, thus I suggest you to research about those from the site itself. But the question 3 is a new question in the site(I believe). And it is to be noted that generally posting too many questions inside a single post is discouraged. $\endgroup$
    – Rishi
    Jun 4, 2021 at 9:52
  • $\begingroup$ @Rishi I have found a related answer but that I didn't understand very well, can u suggest me the answer? $\endgroup$ Jun 7, 2021 at 12:50
  • $\begingroup$ chemistry.stackexchange.com/questions/16145/… This and the the posts on the right side(if you are using desktop mode) or at the bottom(if mobile mode) will clear up your confusion in 1. And 2. $\endgroup$
    – Rishi
    Jun 7, 2021 at 15:22
  • $\begingroup$ physics.stackexchange.com/questions/187269/… This may help as well. $\endgroup$
    – Rishi
    Jun 7, 2021 at 15:23
  • $\begingroup$ It doesn’t make even a teensy bit then, first check out quantum mechanical model of atom first, then Valence Bond theory and then molecular orbital theory(Atleast it worked for me this way) $\endgroup$
    – Rishi
    Jun 7, 2021 at 15:27


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