Chemistry NCERT Exemplar Solutions Class 12th Chapter Eight

Electronic configuration of the given ions is :

$E{u}^{2+}-4f^{7}6s^0$                 

$\begin{array}{l}T{m}^{2+}-4f^{13}6s^0\\ S{m}^{2+}-4f^{6}6s^0\\ T{m}^{3+}-4f^{12}6s^0\end{array}$

$\begin{array}{l}T{b}^{4+}-4f^{7}6s^0\\ Y{b}^{2+}-4f^{14}6s^0\\ D{y}^{3+}-4f^{9}6s^0\\ y{b}^{3+}-4f^{13}6s^0\end{array}$              

Hence, Eu²⁺ and Tb⁴⁺ have half | filled f-orbitals and Yb²⁺ have completely filled f-orbitals.

In 3d-series, all metals except Cu have negative value of $E_{M^{2+}/M}^0$ due to low hydration enthalpy and high I.E and sublimation enthalpy.

71.  (i) - (c); (ii)- (d); (iii)- (b); (iv)- (e)

70.  (i) - (b); (ii)- (d); (iii)- (a); (iv)- (e); (v)- (c)

69.  (i) - (d); (ii)- (a); (iii)- (b); (iv)- (e); (v)- (f)

68.  (i) - (c); (ii)- (a); (iii)- (e); (iv)- (b)

67.  (i) - (c); (ii)- (a); (iii)- (b)