Question

Knowing that the chemistry of lanthanoids (Ln) is dominated by its +3 oxidation state, which of the following statements is incorrect ?
(a) Because of the large size of the Ln(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.
(d) Ln(III) hydroxides are mainly basic in character.

Answer 1

(c) : Ln³⁺ compounds are generally coloured in the solid state as well as in aqueous solution. Colour appears due to presence of unpaired f-electrons which undergo f-f transition.