Find the incorrect comparison of second ionisation energy.

The first ionization enthalpies of $C$,$N$,and $F$ are $1086$,$1402$,and $1681 \, kJ \, mol^{-1}$ respectively. Which of the following values is the most likely first ionization enthalpy of $O$ ($1310$ or $1510 \, kJ \, mol^{-1}$)?

In a group of elements,as the atomic number increases,which of the following is $NOT$ observed?

$A$ large difference between the fourth and fifth ionization energies indicates the presence of

Match the following List-$I$ and List-$II$ and select the correct answer using the codes given below.
List-$I$ (Successive Ionization Enthalpy) $\left( kJ \, mol^{-1} \right)$ List-$II$

Element	$IE_1$	$IE_2$	$IE_3$	Code	Element
$1$	$2080$	$3963$	$6130$	$(a)$	$H$
$2$	$520$	$7297$	$11810$	$(b)$	$Li$
$3$	$900$	$1758$	$14810$	$(c)$	$Be$
$4$	$800$	$2428$	$3660$	$(d)$	$B$
-	-	-	-	$(e)$	$Ne$

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