The first ionisation potential of $Na$ is $5.1 \, eV$. The value of electron gain enthalpy of $Na^{+}$ will be : ............... $eV$

The correct order of the second ionization energy of $C$,$N$,$O$,and $F$ is :-

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

Which of the following statements is incorrect?

Electronic configurations of four elements $A$,$B$,$C$,$D$ are given below:
$A$) $1s^2 2s^2 2p^6 3s^1$
$B$) $1s^2 2s^2 2p^6 3s^2 3p^1$
$C$) $1s^2 2s^2 2p^6 3s^2$
$D$) $1s^2 2s^2 2p^6 3s^2 3p^2$
The correct order of first ionization enthalpy of these elements is:

The atomic number of the element from the following with the lowest $1^{st}$ ionisation enthalpy is: