Vacant d-orbitals in elements allows transfer of electrons after unpairing electrons from s and p orbitals. D- orbitals are present in P and S due to which they can accommodate extra electrons which increases their covalency.

In excited state sulphur has a valency of six due to six unpaired electrons. Similarly in phosphorous it has a valency of 5 in the excited state due to the presence of the 5 unpaired electrons.

For example,

Sulphur configuration: 1s² 2s² 2p⁶ 3s² 3p⁴

Sulphur configuration excited state: 1s² 2s² 2p⁶3s¹3p³3d²

Phosphorous configuration: 1s² 2s² 2p⁶ 3s² 3p³

Phosphorous configuration excited state: 1s² 2s² 2p⁶3s¹ 3p³3d¹