Lv 4
? 發問於 科學及數學化學 · 1 十年前

chem **URGENT!!

Why Si-O bond has higher bond energy than the C-O bond?

1 個解答

  • 1 十年前

    my opinion:

    silicon has vacant low-energy 3d-orbitals, which allows sideway overlapping with oxygen's lone pair in p-orbital. this gives some pi-bond character to the original sigma-bond, in effect strengthens the Si-O bond.

    on the other hand, carbon does not have low-lying orbitals for this kind of interaction. (lowest unoccupied molecular orbital, LUMO, with matched symmetry and orientation is 3p, which is much higher-energy and orbital-mixing would not be efficient).

    of course overlapping of O's 2p with Si's 3d is not very efficient (consider energy difference and size), but it's still more favourable than C-O's sideway overlapping. thus Si-O is somewhat stronger than C-O.

    ... and you can now relate the bond strength to bond energy.