Question

So my question is in the title : Why can s and p orbitals of one atom form hybrid orbitals but the overlapping of one s orbital and one p orbital (perpendicular to the bond axis) of two different atoms don't form a molecular orbital (MO)?

I'm confused because I see both resulting orbitals (hybrid and non-existent MO) as a linear combination of atomic orbitals (LCAO) and that in the case of Molecular orbital theory (MOT), I learned that atomic orbitals of different atoms can interact to form molecular orbital only if they have the same symmetry (and are close in energy) so that their overall overlapping is positive or negative (=non zero).

If someone could explain where I'm wrong or what I see incorrectly, it would be very helpful. Thanks

Answer 1

Hybrid orbitals are formed by combining atomic orbitals within the same atom, resulting in orbitals with different shapes and energies. Molecular orbitals can only form when atomic orbitals of different atoms have the same symmetry and are close in energy.

Step-by-step explanation:

Hybrid orbitals are formed by combining atomic orbitals within the same atom, resulting in orbitals that have different shapes and energies.

On the other hand, the overlapping of one s orbital and one p orbital of different atoms does not form a molecular orbital because the atomic orbitals have different shapes and energies, making their overall overlapping equal to zero.

When two atomic orbitals combine to form hybrid orbitals, they must have the same symmetry and be close in energy to have a non-zero overlap. In the case of molecular orbitals, the atomic orbitals must also have the same symmetry, but the requirement for similar energies is not as strict.