JEE Chemistry 2023 Question with Solution

Given: Inert gases have positive electron gain enthalpy, and the correct order is required.

Find: The correct increasing order of positive electron gain enthalpy for He, Xe, Kr, and Ne.

From the solution, the tabulated values are:

• He: $+48 \, \text{kJ/mol}$
• Ne: $+116 \, \text{kJ/mol}$
• Kr: $+96 \, \text{kJ/mol}$
• Xe: $+77 \, \text{kJ/mol}$

Arranging these in increasing order:

$$\text{He} < \text{Xe} < \text{Kr} < \text{Ne}$$

Therefore, the correct option is B.

Given: Electron gain enthalpy refers to the energy change when an atom gains an electron.

Find: The correct order among inert gases.

Inert gases have closed electronic configurations, so addition of an electron is unfavorable and electron gain enthalpy is positive. As atomic size increases, electron-electron repulsion for the incoming electron decreases, so the positive value becomes less extreme for larger atoms.

Using the values shown in the solution:

$$\text{He} = +48, \quad \text{Xe} = +77, \quad \text{Kr} = +96, \quad \text{Ne} = +116 \, \text{kJ/mol}$$

Hence the order is:

$$\text{He} < \text{Xe} < \text{Kr} < \text{Ne}$$

So, the correct option is B. The answer key and option text on the page disagree with the actual option labels; the solution identifies this ordering as option B.