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) decrease 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

Answer 1

Answer: (B)

Due to poor shielding effect of $f$ subshell ionic radius of $Ln ^{+3}$ decreases as atomic number increases. If an element has unpaired electron then it shows colour. lanthanum are basic in nature. Their's compounds are predominantly ionic due to large size of cation.