Question

Which one of the following lanthanoids does not form $M{O}_2?$
($M$ = Lanthanoid element)

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

Answer 1

The correct option is B $Yb$

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

$Yb$ has fully-filled $4f$ orbital, it will require very large amount of energy to reach $+4$ oxidation state. Hence, $Yb$ does not form $M{O}_2$ type oxide.