The ionization energy of nitrogen is more than that of oxygen because

From the following elements,which of them has the highest second ionisation potential?

Given below are two statements:
Statement $I$: The decrease in first ionization enthalpy from $B$ to $Al$ is much larger than that from $Al$ to $Ga$.
Statement $II$: The $d$ orbitals in $Ga$ are completely filled.
In the light of the above statements,choose the most appropriate answer from the options given below:

The first ionization enthalpy $(\Delta_{i} H)$ values of the third period elements,$Na, Mg$ and $Si$ are respectively $496, 737$ and $786 \, kJ \, mol^{-1}$. Predict whether the first $\Delta_{i} H$ value for $Al$ will be more close to $575$ or $760 \, kJ \, mol^{-1}$? Justify your answer.

Which of the following statements is correct about ionization potential?

The first four $I.E.$ values of an element are $284, 412, 656$ and $3210 \ kJ \ mol^{-1}$. The number of valence electrons in the element are