Lanthanoid ions with $4 \mathrm{f}^7$ configuration are :

(A) $\mathrm{Eu}^{2+}$

(B) $\mathrm{Gd}^{3+}$

(C) $\mathrm{Eu}^{3+}$

(D) $\mathrm{Tb}^{3+}$

(E) $ \mathrm{Sm}^{2+}$

Choose the correct answer from the options given below :

The electronic configuration of Einsteinium is :

(Given atomic number of Einsteinium $$=99$$)

Give below are two statements :

Statement I : The higher oxidation states are more stable down the group among transition elements unlike p-block elements.

Statement II : Copper can not liberate hydrogen from weak acids.

In the light of the above statements, choose the correct answer from the options given below :

The electronic configuration of $$\mathrm{Cu}(\mathrm{II})$$ is $$3 \mathrm{~d}^9$$ whereas that of $$\mathrm{Cu}(\mathrm{I})$$ is $$3 \mathrm{~d}^{10}$$. Which of the following is correct?