Question

Identify the incorrect statement among the following.

• A. Lanthanide contraction is the accumulation of successive shrinkages
• B. As a result of Lanthanide contraction, the size of $4d$ series of transition metals have same size that of the $5d$ series of elements of same group
• C. Ionization energy of 4d series elements is higher than corresponding 5d series elements of same group
• D. Lanthanide contraction is the cause of lower ionisation energy of $Sn$ than $Pb$

Answer 1

The correct option is C Ionization energy of 4d series elements is higher than corresponding 5d series elements of same group

As a result of lanthanoid contraction, the properties of the $4d$ series of the transition elements have certain similarities with the $5d$ series of elements.
Due to the poor shielding effect of 4f-electrons (lanthanide contraction ) in $Pb$ the effective nuclear charge increases and hence it has high ionisation energy
The size of $4d$ series of transition metals is same as that of the $5d$ series of elements of same group this is due to the lanthanoid contraction.
Ionization energy of 5d elements are higher than 4d elements due to the greater effective nuclear charge acting on outermost shell electrons due to poor shielding of 4f electrons.