The energy required to remove an electron of a gaseous atom from its ground state is called

The first ionization energy of magnesium is smaller as compared to that of elements $X$ and $Y$,but higher than that of $Z$. The elements $X$,$Y$ and $Z$,respectively,are :

The successive ionization enthalpy values for an unknown element are $\Delta_i H_1 = 899 \ kJ/mol$,$\Delta_i H_2 = 1757 \ kJ/mol$,$\Delta_i H_3 = 14847 \ kJ/mol$,and $\Delta_i H_4 = 17948 \ kJ/mol$. To which group of the periodic table does this element belong?

The first ionization enthalpy values (in $kJ\,mol^{-1}$) of group $13$ elements are :

$B$	$801$
$Al$	$577$
$Ga$	$579$
$In$	$558$
$Tl$	$589$

How would you explain this deviation from the general trend?

Which of the following elements has the highest first ionization enthalpy?

Given below are two statements:
Statement $I$: The second ionization enthalpy of $B$,$Al$ and $Ga$ is in the order of $B > Al > Ga$.
Statement $II$: The correct order in terms of first ionization enthalpy is $Si < Ge < Pb < Sn$.