Q. The correct order of the mobility of the alkali metal ions in aqueous solution is :
A) Li⁺ > Na⁺ > K⁺ > Rb⁺
B) Na⁺ > K⁺ > Rb⁺ > Li⁺
C) K⁺ > Rb⁺ > Na⁺ > Li⁺
D) Rb⁺ > K⁺ > Na⁺ > Li⁺
Explanation
[Solution from source] The smaller the ion, the more strongly it is hydrated, so Li⁺ carries the largest hydration shell and moves slowest. Hydrated size decreases down the group, so mobility in water is Rb⁺ > K⁺ > Na⁺ > Li⁺, the reverse of the order of bare ionic size. Answer (4).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.