# 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?

Jan 30, 2017

Sulfur can use its $\text{3d}$ orbitals to form new hybrid $\text{sp"^3"d}$ and ${\text{sp"^3"d}}^{2}$ 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 $\text{2s}$ electron to an empty $\text{2p}$ orbital and mixing them to form new ${\text{sp}}^{3}$ hybrid orbitals.

In the same way, sulfur can promote its $\text{3s}$ and $\text{3p}$ electrons to empty $\text{3d}$ orbitals and mixing them to form new hybrid orbitals.

The ground state electron configuration of $\text{S}$ is ${\text{[Ne] 3s"^2 "3p}}^{4}$.

Promoting a $\text{3s}$ and a $\text{3p}$ electron to the $\text{3d}$ level gives the excited state shown below.

These orbitals can be mixed to form six new hybrid ${\text{sp"^3"d}}^{2}$ orbitals, each containing one electron.

(From www.alyvea.com)

These six orbitals can then overlap with the half-filled $\text{2p}$ orbital of $\text{F}$ to form ${\text{SF}}_{6}$.