The correct order of ionisation energy of $C$,$N$,$O$,and $F$ is

Ionization potential is lowest for

Which of the following represents the correct decreasing order of the first ionization enthalpy of $Ba, Sr, Ca,$ and $Mg$?

Identify the element having the highest ionization enthalpy.

The first ionization enthalpies of $Li$,$Be$,and $C$ are $520$,$899$,and $1086 \ kJ \ mol^{-1}$ respectively. Which of the values $800$ or $900 \ kJ \ mol^{-1}$ is more likely for the first ionization enthalpy of $B$? Why?

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