The element with a very high ionization enthalpy but zero electron gain enthalpy is ....

Consider the following statements:
$(I)$ Ionic mobility of hydrated $Li^+$ is greater than that of hydrated $Na^+$.
$(II)$ $IE_1$ of $P$ atom is higher than that of $S$ atom,while $IE_2$ of $S$ atom is higher than that of $P$ atom.
$(III)$ Lithium is a strong reducing agent in aqueous medium.
Which of the above statements is/are correct?

Choose the correct statement.

Which of the following statements is incorrect?

Which of the following sequences represents the atomic numbers of only representative elements?

Given below are two statements $:$
Statement $(I) :$ The radii of isoelectronic species increase in the order $Mg^{2+} < Na^{+} < F^{-} < O^{2-}$.
Statement $(II) :$ The magnitude of electron gain enthalpy of halogens decreases in the order $Cl > F > Br > I$.
In the light of the above statements,choose the most appropriate answer from the options given below $:$