MHT CET202523 Apr 2025Morning ShiftChemistryd and f Block ElementsActual
Which element from following has largest ionic size in +3 state ?
Options
- APr
- BSm
- CLa
- DYb
Correct answer
C. La
Step-by-step solution
The lanthanide contraction explains why La ³⁺ has the largest ionic radius among the given +3 lanthanide ions. The 4f electrons provide poor shielding from increasing nuclear charge across the lanthanide series, causing a gradual decrease in ionic radii from lanthanum to ytterbium. Among La ³⁺ (Z=57), Pr ³⁺ (Z=59), Sm ³⁺ (Z=62), and Yb ³⁺ (Z=70), lanthanum appears first in the series and therefore has the largest ionic size in the +3 oxidation state. The ionic radius decreases progressively as La ³⁺ > Pr ³⁺ > Sm ³⁺