Which of the following has the lowest first ionisation potential?

Among the second period elements,the actual ionization enthalpies are in the order $Li < B < Be < C < O < N < F < Ne$. Explain why:
$(i)$ $Be$ has higher $\Delta_{i}H$ than $B$
$(ii)$ $O$ has lower $\Delta_{i}H$ than $N$ and $F$?

Discuss and compare the trend in ionisation enthalpy of the elements of group-$1$ with those of group-$17$ elements.

Which of the following electronic configurations is associated with the biggest jump between the second and third ionization energies?

Which of the following has the minimum ionization energy?

The correct order of second ionization potential of carbon,nitrogen,oxygen and fluorine is