Periodic Table and Periodicity

Which pair of elements has maximum
electronegativity difference?

Which has least covalent radius?

Which have melting point below \(500^{\circ} \mathrm{C}\) ?

Correct order of bond dissociation energy

Assertion (A) Electron gain enthalpy
becomes less negative as we go down a group.
Reason (R) Size of the atom increases on
going down the group and the added electron
would be farther away from the nucleus.

The ionic radii \((\mathop A\limits^o)\) of \(\mathrm{C}^{4-}\) and \(\mathrm{O}^{2-}\) respectively are 2.60 and 1.40. The ionic radius of the isoelectronic ion \(\mathrm{N}^{3-}\) would be

In which of the following arrangements, the
order is not strictly according to the property
written against it?