Which of the following has the highest first ionisation energy?

The second ionization potential of elements is invariably higher than the first ionization potential because:

How would you explain the fact that the first ionization enthalpy of sodium is lower than that of magnesium but its second ionization enthalpy is higher than that of magnesium?

$A \to A^{+} + e, E_{1}$ and $A^{+} \to A^{2+} + e, E_{2}$. The energy required to pull out the two electrons are $E_{1}$ and $E_{2}$ respectively. The correct relationship between the two energies is:

Given below are two statements:
Statement $I$: The first ionization energy of $Pb$ is greater than that of $Sn$.
Statement $II$: The first ionization energy of $Ge$ is greater than that of $Si$.
In the light of the above statements,choose the correct answer from the options given below:

The first ionization enthalpy of $Na$,$Mg$ and $Si$,respectively,are: $496, 737$ and $786 \ kJ \ mol^{-1}$. The first ionization enthalpy $(kJ \ mol^{-1})$ of $Al$ is