Question

Which of the following sequence will show an increase in ionisation enthalpy?

• A. From $C$ to $Si$
• B. From $Si$ to $Ge$
• C. From $Ge$ to $Sn$
• D. From $Sn$ to $Pb$

Answer 1

The correct option is D From $Sn$ to $Pb$

In general, ionisation enthalpy decrease down the group due to increase in size and lesser nuclear charge.
On going down the group, there is a considerable decrease in ionisation enthapy from C to Si whereas only a small decrease from Si to Sn and there is slight increase in ionisation value from Sn to Pb. This is due to the consequence of poor shielding effects of intervening d and f-orbitals and increase in size of the atom. Due to very poor shielding effect the nuclear charge doesn't decrease much in heavier atom and thus, result in increase in ionisation from Sn to Pb