Explain why is there a phenomenal decrease in ionisation enthalypy for canbon to sillican ?

Explanation

On moving from carbon to silican 1. size of Si increases due to the addition of a new shell, 2. effective nuclear charge on Si increases due to increase in the number of protons 3. shielding effect increases due to increases in the number of 1. and 2. Thus, there is a phenomenal drcrease in ionisation enthalpy as we move from carbon to silicon.