If $X$ and $Y$ are the second ionisation potentials of alkali and alkaline earth metals of the same period,then:

Given below are two statements: One is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: The first ionization enthalpy of $O$ is lower than that of $N$ and $F$.
Reason $R$: The loss of an electron from $O$ leads to a stable half-filled $p$ orbital.
In light of the above statements, choose the most appropriate answer from the options given below:

In which of the following pairs does the molecule have a higher $IE_1$ value compared to its corresponding atom?

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?

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