Question

The first ionisation energies of silicon and sulphur are lower than that of phosphorus.
Explain

Answer 1

Answer:

It is seen that the ionisation energy of silicon and sulphur are lower as compared to phosphorous because phosphorous is comparatively smaller in size , therefore its nuclear charge is more and due to this energy required to remove electron is higher.

Explanation:

Answer 2

Answer:

The half-filled and fully filled orbitals are more stable than partially filled orbitals. Thus, phosphorus with exactly half-filled p orbitals, is more stable than silicon and sulphur, with partially filled orbitals. Hence, ionisation energy of phosphorus is larger than that of silicon and sulphur.