Assertion : Compounds of ${\mathrm{Hg}}^{2+}$ ions having an ionic radius of 116 pm are move covalent in character

                   than those of ${\mathrm{Ca}}^{2+}$ ions with almost identical size (114 pm) and the same charge.

Reason : For two ions of the same size and charge, one with an (n-1)${\mathrm{d}}^{10}{\mathrm{ns}}^0.$ electronic configuration

                 will be more polarizing than a cation with an (n-1)${\mathrm{s}}^2$ (n-1)${\mathrm{p}}^6{\mathrm{ns}}^0,$ electronic configuration.

1. If both the assertion and the reason are true and the reason is a correct explanation of the assertion
2. If both the assertion and reason are true but the reason is not a correct explanation of the assertion
3. If the assertion is true but the reason is false
4. If both the assertion and reason are false

Assertion : In tetrahedral hybridisation i.e., in ${\mathrm{sp}}^3$ hybridisation all p-orbitals are involved and no

                   p-orbital is left for coming with $\mathrm{\pi }$-bonds.

Reason : Central atom can not form double bonds in the molecules or species having ${\mathrm{sp}}^3$hybridisation.

Assertion : $\mathrm{}\mathcal{}$ F bond angle P = bond angle Q but not precisely $90°.$

Reason : The molecule is slight bent T-shaped and there is repulsion between lone pairs of electrons.

Assertion : ${\mathrm{N}}_2{{\mathrm{F}}_3}^{+}$ is planar at each nitrogen atom.

Reason : ${\mathrm{N}}_3\mathrm{H},$ the bond angle $\mathrm{H}‐\mathrm{N}‐\mathrm{N}$ is $120°$ and both the $\mathrm{N}‐\mathrm{H}$ bond lengths are not equal.

Assertion : Carbon has unique ability to form $\mathrm{p\pi }-\mathrm{p\pi }$ multiple bonds with itself and with other

                  atoms of small size and high electronegativity.

Reason : Heavier elements of group ${14}^{\mathrm{th}}$ do not form $\mathrm{p\pi }-\mathrm{p\pi }$ multiple bonds with itself because

               their atomic orbitals are too large and diffuse to have effective overlapping.

Select the correct option based on statements below:

Assertion : ${\mathrm{NO}}^{+}$ and ${\mathrm{CN}}^{-}$ both have same bond order and magnetism

Reason : ${\mathrm{NO}}^{+}$ and ${\mathrm{CN}}^{-}$ are isoelectornic species.

Assertion : Crystals of hydrated calcium sulphate $\left(\mathrm{gypsum} : {\mathrm{CaSO}}_4, 2{\mathrm{H}}_2\mathrm{O}\right)$ are soft and easily cleaved.

Reason : Crystals of anhydrous calcium sulphate $\left(\mathrm{anhydrite} : {\mathrm{CaSO}}_4\right)$ are very hard and very difficult

               to cleave.

 When two atoms combine to form a molecule, energy is: 

Which of the following compounds possesses the highest melting point?

1. BeCl₂

2. MgCl₂

3. CaCl₂

4. SrCl₂