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Answer the following.
Which trivalent ion has maximum size in the Lanthanoid series i.e. Lanthanum ion ( ) to Lutetium…
Which trivalent ion has maximum size in the Lanthanoid series i.e. Lanthanum ion ($\text{La}^{3+}$) to Lutetium ion ($\text{Lu}^{3+}$)?
(at. no. of Lanthanum = 57 and Lutetium = 71)
Answer
Answer
AI$\mathrm{La^{3+}}$ has the maximum size, because of the lanthanoid contraction: the ionic radius decreases steadily from $\mathrm{La^{3+}}$ to $\mathrm{Lu^{3+}}$ as the poorly shielding 4f electrons let the nuclear charge increase.
From ISC 2019 Chemistry Paper 1, question 1(d)(i)(1).