Question

Given below are two statements:
Statement I: Fluorine has most negative electron gain enthalpy in its group.
Statement II: Oxygen has least negative electron gain enthalpy in its group.
In the light of the above statements, choose the most appropriate from the options given below.

• A. Both Statement I and Statement II are true
• B. Statement I is true but Statement II is false
• C. Both Statement I and Statement II are false
• D. Statement I is false but Statement II is true

Answer 1

The Correct Option is D

Analysis of periodic trends requires understanding electron gain enthalpy within groups. The electron gain enthalpy is the energy change upon adding an electron to a neutral gaseous atom. Generally, across a period, this value becomes more negative. This trend is less consistent within groups. For Group 17 (halogens), the electron gain enthalpy of chlorine is more negative than that of fluorine. This is attributed to fluorine's smaller atomic radius, which leads to greater electron-electron repulsion within its electron cloud, making the addition of an electron less energetically favorable compared to chlorine. Consequently, Statement I, "Fluorine has the most negative electron gain enthalpy in its group," is false.

Regarding Statement II, "Oxygen has the least negative electron gain enthalpy in its group," oxygen belongs to Group 16. Similar to the case with fluorine, oxygen's relatively small atomic size results in significant electron-electron repulsion when an additional electron is introduced. This repulsion reduces the net energy released, meaning oxygen has the least negative electron gain enthalpy within its group. Therefore, Statement II is true.

Based on the preceding explanations, the correct conclusion is that Statement I is false, and Statement II is true.