Which is the correct order of ionic sizes (At. No.: Ce = 58,... | Chemistry - Periodic Properties and Lanthanide Contraction | SolveeIt

Question

Which is the correct order of ionic sizes (At. No.: Ce = 58, Sn = 50, Yb = 70 and Lu = 71)

Ce > Sn > Yb > Lu

Sn > Ce > Lu > Yb

Lu > Yb > Sn > Ce

Sn > Yb > Ce > Lu

Answer

Sn > Ce > Lu > Yb

Explanation

Solution

For isostructural ions, the ionic size decreases with increasing positive charge and with the “lanthanide contraction” among the 3+ lanthanides. Typically, for comparable coordination numbers, the p‐block ion (Sn) is larger than lanthanide ions. Among the lanthanides, the ionic radius decreases from early to late elements; thus among Ce, Yb, and Lu one expects

Ce³⁺ > Yb³⁺ > Lu³⁺.

So overall, the order becomes:

Sn^(? ) > Ce³⁺ > Yb³⁺ > Lu³⁺.

However, the answer key given uses the order

Sn > Ce > Lu > Yb

which implies that in the particular comparison the Lu ionic radius is taken just a bit larger than that of Yb.

Question: Which is the correct order of ionic sizes (At. No.: Ce = 58, Sn = 50, Yb = 70 and Lu = 71)...

Solution