Question

Oxygen reacts with fluorine to form only `OF_2`, but sulphur which is in the same Group 16 as oxygen, reacts with fluorine to form `SF_2`, `SF_4` and `SF_6`. Why is this?

Answer 1

Sulfur can use its `"3d"` orbitals to form new hybrid `"sp"^3"d"` and `"sp"^3"d"^2` orbitals.

Explanation:

The diagram below shows the order of orbital energy levels in an atom.

Recall that carbon can form four equivalent orbitals by promoting a `"2s"` electron to an empty `"2p"` orbital and mixing them to form new `"sp"^3` hybrid orbitals.

(From CHROMacademy)

In the same way, sulfur can promote its `"3s"` and `"3p"` electrons to empty `"3d"` orbitals and mixing them to form new hybrid orbitals.

The ground state electron configuration of `"S"` is `"[Ne] 3s"^2 "3p"^4`.

Promoting a `"3s"` and a `"3p"` electron to the `"3d"` level gives the excited state shown below.

These orbitals can be mixed to form six new hybrid `"sp"^3"d"^2` orbitals, each containing one electron.

(From www.alyvea.com)

These six orbitals can then overlap with the half-filled `"2p"` orbital of `"F"` to form `"SF"_6`.