Question

Inert gases have positive electron gain enthalpy Its correct order is

• A. $He < Ne < Kr _{ r }< Xe _{ e }$
• B. $He < Xe < Kr < Ne$
• C. $He < Kr < Xe _{ e }< Ne$
• D. $Xe < Kr < Ne < He$

Answer 1

The Correct Option is B

To understand why inert gases have a positive electron gain enthalpy and the order among them, let's delve into the basic concepts of electron gain enthalpy and characteristics of inert gases.

Electron Gain Enthalpy: When an atom gains an electron, the energy change that occurs is measured as electron gain enthalpy. It can either be endothermic (requiring energy) or exothermic (releasing energy), predominantly exothermic. However, for inert gases, it is positive (endothermic) because adding an electron to their already stable configuration requires energy.

Inert Gases Overview: The inert gases, also known as noble gases, have a complete outer electron shell, making them highly stable and generally unreactive. The electron configuration for inert gases is characterized by a filled outer shell (ns²np⁶ except for Helium, which is 1s²).

The order of positive electron gain enthalpy among the inert gases arises from their size and the effective nuclear charge. To determine the correct order:

1. Helium (He) has the least positive electron gain enthalpy because its small size allows the addition of an electron with lesser energy requirement.
2. Xenon (Xe) comes next due to its larger size, which reduces nuclear charge efficacy, requiring more energy for adding an electron.
3. Krypton (Kr) follows Xenon in this order. Despite being smaller than xenon, its nuclear charge presence requires slightly less energy than xenon.
4. Neon (Ne) has the most positive electron gain enthalpy due to its small size with complete and stable outer shells, making it most resistant to accepting an additional electron without energy input.

Thus, the correct order of electron gain enthalpy is \(He < Xe < Kr < Ne\).

Conclusion: Based on the concept of electron gain enthalpy and characteristics of inert gases, we conclude that the correct order provided is \(He < Xe < Kr < Ne\). Accordingly, the correct answer is; He < Xe < Kr < Ne.