Question

Assertion (A): Noble gases have positive electron gain enthalpy. Reason (R): Noble gases have stable closed-shell electronic configuration.

(a) Both (A) and (R) are true, and (R) is the correct explanation of (A).

(b) Both (A) and (R) are true, but (R) is not the correct explanation of (A).

(c) (A) is true, but (R) is false.

(d) (A) is false, but (R) is true.

Answer 1

The assertion that noble gases have positive electron gain enthalpy is false, while the reason that they have a stable closed-shell electronic configuration is true. Noble gases do not easily gain electrons due to their stable, full valence shells, complying with the octet rule.

Step-by-step explanation:

The question revolves around the concept of electron gain enthalpy in the context of noble gases. Assertion (A) states that noble gases have positive electron gain enthalpy, which is false because they already possess a stable, filled valence electron shell, making it energetically unfavorable and difficult to add an additional electron. Reason (R) says that noble gases have a stable closed-shell electronic configuration, which is true and precisely why their electron gain enthalpy is not positive since their filled valence shells are already energetically optimal and do not tend to attract extra electrons without the application of high energy conditions.

Electron gain enthalpy (EA) is generally more negative as we move from left to right across a period in the periodic table. The noble gases, found in group 18, are an exception to this trend due to their complete valence shell configuration. The octet rule also indicates that atoms strive to achieve the stable noble gas configuration, which the noble gases naturally possess. Overall, the noble gases' reluctance to form compounds exemplifies the stability provided by their full valence shells.