Knowing that the Chemistry of lanthanoids (Ln) is dominated by its +3 oxidation state, which of the following statements in incorrect ?
- (A)Because of the large size of the (III) ions the bonding in its compounds is predominantly ionic in character.
- (B)The ionic sizes of Ln (III) decrease in general with increasing atomic number.
- (C)Ln (III) compounds are generally colourless.✓ Correct
- (D)Ln (III) hydroxides are mainly basic in character.
Answer: (C)
Solution
Lanthanoid(III) ions generally carry partly filled shells whose transitions give their compounds characteristic colours, so the claim that Ln(III) compounds are generally colourless is the incorrect statement. The others hold true: the large Ln(III) ions bond in a mainly ionic way, their sizes shrink steadily with rising atomic number through the lanthanoid contraction, and their hydroxides are predominantly basic.
JEE Main · 2009 · 12 Apr 2009 · Offline · Single correct option