Which is the correct order of second ionization potential of $C, N, O$ and $F$ in the following?

The successive ionisation enthalpies of an element $X$ in $(kJ \ mol^{-1})$ are $1012$,$1907$,$2955$,$4955$,$6275$ and $21,260$ respectively. The element $X$ is:

$X_{(g)} \to X^{+}_{(g)} + e^-$,$\Delta H = +720 \ kJ \ mol^{-1}$
Calculate the amount of energy required to convert $110 \ mg$ of $X$ atom in gaseous state into $X^{+}$ ion .................... $kJ$ (Atomic weight for $X = 7 \ g \ mol^{-1}$)

For an element,the values of $IP_1, IP_2, IP_3, IP_4$ and $IP_5$ are $7.1, 14.3, 34.5, 46.8$ and $162.2 \ eV$ respectively. Which of the following is the most likely element?

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

Calculate the energy required to convert all atoms in $4.8 \ g$ of $Mg$ to $Mg^{2+}$ in the vapour state. $IE_1$ and $IE_2$ of $Mg$ are $740 \ kJ / mol$ and $1450 \ kJ / mol$ respectively.