Question

Knowing that the chemistry of lanthanoids (Ln) is dominated by its +3 oxidation state, which of the following statements is incorrect?

• A. The ionic size of Ln(III) decreases in general with increasing atomic number
• B. Ln(III) compounds are generally colourless
• C. Ln(III) hydroxide are mainly basic in character
• D. Because of the large size of the Ln(III) ions the bonding in its compounds is predominantly ionic in character

Hint:

Colour in lanthanoids arises from: f--f electronic transitions

Answer 1

The Correct Option is B

Step 1: Lanthanoid ionic radii decrease gradually due to lanthanide contraction.
Step 2: Most Ln(III) compounds are coloured due to f--f electronic transitions (except f⁰ and f¹4 cases).
Step 3: Ln(III) hydroxides are basic and their compounds are largely ionic.