Mercury is the only metal which is liquid at $0 \, ^oC$. This is due to its:

The first ionization enthalpies of four consecutive elements present in the second period of the periodic table are $8.3, 11.3, 14.5$ and $13.6 \ eV,$ respectively. Which one of the following is the first ionization enthalpy of nitrogen?

Assertion $(A)$: $16$th group elements have higher ionisation enthalpy values than $15$th group elements in the corresponding periods.
Reason $(R)$: $15$th group elements have half-filled stable electronic configurations.

Which one of the following is the correct order of the second ionisation potential of $Na$,$Ne$,$Mg$,and $Al$?

The set representing the correct order of first ionisation potential is

Ionization potential is lowest for