Question

Common oxidation state of $f$ -block elements is $III$. The other stable oxidation states of ${ }^{63} Eu$ and ${ }^{65} Tb$ are respectively

• A. II, IV
• B. IV,II
• C. II, V
• D. V , I

Answer 1

Answer: (A)

Common oxidation state of $f$ - block elements is $(+) 3$, but $Eu$ and $Tb$ can also show $(+) 2$ and $(+) 4$ oxidation states respectively because of $4 \,f^{7}$ and $4\, f^{9}$ electrons in $4\,f$ -subshell respectively.