Question

Match the following \[ \begin{array}{|c|c|} \hline \text{List-I} & \text{List-II} \\ \hline \text{A. Co, Ni} & \text{I. Electronegativity} \\ \text{B. K, Ba} & \text{II. Electron gain enthalpy} \\ \text{C. N, Cl} & \text{III. Metallic radius} \\ \text{D. Ar, Kr} & \text{IV. Standard reduction potential (-ve)} \\ \hline \end{array} \] The correct answer is

• A. A-III, B-I, C-IV, D-II
• B. A-IV, B-III, C-II, D-I
• C. A-IV, B-III, C-I, D-II
• D. A-III, B-IV, C-I, D-II

Hint:

Transition elements often show anomalous similarities due to poor shielding by \(d\)-electrons. Noble gases usually possess positive electron gain enthalpy because additional electrons must enter higher energy orbitals.

Answer 1

The Correct Option is D

Concept: Matching questions are solved by identifying similar periodic properties between given pairs of elements. We analyse each pair carefully.

Step 1: Analyse pair A: Co, Ni Cobalt and nickel have nearly identical: Metallic radii This happens because of poor shielding effect of \(3d\) electrons. Thus: \[ A \rightarrow III \]

Step 2: Analyse pair B: K, Ba Potassium and barium possess nearly same: Standard reduction potential Both have highly negative reduction potentials. Thus: \[ B \rightarrow IV \]

Step 3: Analyse pair C: N, Cl Nitrogen and chlorine have almost same: Electronegativity Approximate values: \[ \chi_N \approx 3.0 \] \[ \chi_{Cl} \approx 3.0 \] Thus: \[ C \rightarrow I \]

Step 4: Analyse pair D: Ar, Kr Argon and krypton have positive electron gain enthalpies. Their electron gain enthalpy behaviour is similar because noble gases possess stable electronic configurations. Thus: \[ D \rightarrow II \]

Step 5: Write final matching. Therefore: \[ A-III,\quad B-IV,\quad C-I,\quad D-II \] Hence the correct option is: \[ \boxed{(D)} \]