Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A): The first ionization enthalpy of $3\mathrm{d}$ series elements is more than that of group $2$ metals

Reason (R): In $3\mathrm{d}$ series of elements successive filling of $\mathrm{d}$-orbitals takes place.

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

Which of the following elements have half-filled f-orbitals in their ground state ?
(Given : atomic number $\mathrm{Sm}-62;\mathrm{Eu}=63;\mathrm{Tb}=65;\mathrm{Gd}=64,\mathrm{Pm}=61$)

Choose the correct answer from the options given below :

Highest oxidation state of $\mathrm{Mn}$ is exhibited in ${\mathrm{Mn}}_2{\mathrm{O}}_7$. The correct statements about ${\mathrm{Mn}}_2{\mathrm{O}}_7$ are

(A) $\mathrm{Mn}$ is tetrahedrally surrounded by oxygen atoms
(B) $\mathrm{Mn}$ is octahedrally surrounded by oxygen atoms
(C) Contains $\mathrm{Mn}-\mathrm{O}-\mathrm{Mn}$ bridge
(D) Contains $\mathrm{Mn}-\mathrm{Mn}$ bond.

Choose the correct answer from the options given below

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : ${\mathrm{Cu}}^{2+}$ in water is more stable than ${\mathrm{Cu}}^{+}$.
Reason (R) : Enthalpy of hydration for ${\mathrm{Cu}}^{2+}$ is much less than that of ${\mathrm{Cu}}^{+}$.

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