Question

Which one of the following lanthanoids does not form $M{O}_2$ ?

(M is lanthanoid metal)

JEE MAINS 2021

• A. $Dy$
• B. $Yb$
• C. $Nd$
• D. $Pr$

Answer 1

The correct option is B $Yb$

$Nd\left(60\right)=\left[Xe\right]4f^{4}6s^2$
$Pr\left(59\right)=\left[Xe\right]4f^{3}6s^2$
$Dy\left(66\right)=\left[Xe\right]4f^{10}6s^2$
$Yb\left(70\right)=\left[Xe\right]4f^{14}6s^2$

$Y{b}^{+2}$ has fully-filled $4f$ orbital, it will require very large amount of energy to reach $+4$ oxidation state and hence does not form $M{O}_2$.