The first ionisation enthalpies for three elements are $1314$,$1680$ and $2080 \, kJ \, mol^{-1}$,respectively. The correct sequence of the elements is

Which of the following statements is incorrect?

For $Mg$,the values of $\Delta_iH_1$ and $\Delta_iH_2$ are $178 \, kcal \, mol^{-1}$ and $348 \, kcal \, mol^{-1}$ respectively. The enthalpy change for the reaction $Mg \to Mg^{2+} + 2e^-$ is ............. $kcal \, mol^{-1}$.

Discuss the trend of the first ionisation enthalpy in the same period and explain why it occurs.

In which of the following electronic configurations of an element is there a very large difference between the second and third ionization energy?

The first ionisation potential $(IP)$ of the elements $Na$,$Mg$,$Si$,$P$,$Cl$ and $Ar$ are $5.14$,$7.65$,$8.15$,$10.49$,$12.97$ and $15.76 \ eV$,respectively. The $IP$ (in $eV$) of $K$ is closest to