Match List-I with List-II.

Choose the correct answer from the options given below :

In periodic-property matching questions, first recall how each property varies and then find the description that matches this trend.

Case A: Second ionisation enthalpy (IE2)
• For an alkali-metal atom the first electron is removed from the $$ns^{1}$$ subshell, but the second electron must be removed from the stable noble-gas core $$ns^{0}$$ configuration, making IE2 extraordinarily high.
• Hence the correct description is “exceptionally high when removal produces a noble-gas configuration”.
⇒ (A) → (IV)

Case B: Electron-gain enthalpy (electron affinity)
• Within a group, added electrons enter the same type of subshell but the atomic size increases, lessening the effective nuclear attraction.
• Therefore the energy released (numerically the negativity of the value) becomes smaller in magnitude; i.e. it becomes “less negative” down the group.
⇒ (B) → (I)

Case C: Atomic radius
• Across a period the nuclear charge increases while the electrons are added to the same principal shell, pulling the electronic cloud closer to the nucleus.
• Consequently the atomic radius decreases from left to right in a period.
⇒ (C) → (II)

Case D: Electropositive (metallic) character
• Down any main group the outer electrons experience more shielding and are held less tightly, so the tendency to lose electrons (electropositivity) increases.
⇒ (D) → (III)

The complete matching is:
(A) - (IV), (B) - ( I), (C) - (II), (D) - (III)

Therefore the correct option is:
Option A which is: (A)-(IV), (B)-(I), (C)-(II), (D)-(III)