Question

Which of the following sets will have highest hydration enthalpy and highest ionic radius ?

• A. $Na$ and $Li$
• B. $Li$ and $Rb$
• C. $K$ and $Na$
• D. $Cs$ and $Na$

Answer 1

Answer: (B)

As the atomic/ionic size increases, hydration enthalpy decreases. On moving downwards in a group, since ionic/atomic radii increases, thus hydration enthalpy decreases. Hence, among alkali metals Li has the highest hydration enthalpy while Rb has the highest ionic radius