(B) The chemistry of lanthanoids is dominated by the $+3$ oxidation state. Most $Ln^{3+}$ ions contain unpaired $f$-electrons,which undergo $f-f$ tran

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$Ln(III)$ compounds are generally colourless.

(B) The chemistry of lanthanoids is dominated by the $+3$ oxidation state. Most $Ln^{3+}$ ions contain unpaired $f$-electrons,which undergo $f-f$ transitions,making them coloured. Therefore,the statement that $Ln(III)$ compounds are generally colourless is incorrect. $La^{3+}$ $(f^0)$ and $Lu^{3+}$ $(f^{14})$ are colourless,but most others are coloured.

Class 12 Chemistry The d- and f-Block Elements Lanthanoids and Actinoids

Easy

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

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A
The ionic size of $Ln(III)$ ions decreases in general with increasing atomic number.
B
$Ln(III)$ compounds are generally colourless.
C
$Ln(III)$ hydroxides 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.