The Question is from neet-chemistry classification-of-elements , and it was created by the author Mr. S M HUSSAIN

Question

The first ionization enthalpy of inert gases is exceptionally high. Which factor contributes LEAST to this high ionization enthalpy?

Mr. S M HUSSAIN · Accepted Answer

## CORE INFORMATION
✓ **Answer**: D
## CONCEPT FRAMEWORK
 **Primary Concept**: Ionization enthalpy and its dependence on atomic structure.
 **Related Topics**: Electronic configuration, effective nuclear charge, atomic size, shielding effect.
 **Prerequisites**: Understanding of electronic shell structure, periodic trends, and Coulomb's law.
## SOLUTION PATHWAY
**Given Information**:
The question asks which factor contributes LEAST to the high first ionization enthalpy of inert gases.
**Method & Steps**:
1. Analyze the factors affecting ionization enthalpy.
  Reasoning: Ionization enthalpy is the energy required to remove an electron from a gaseous atom. It's influenced by several factors: effective nuclear charge ($Z_{eff}$), atomic size, and electronic configuration.
  Formula/Rule:  Ionization enthalpy is directly proportional to $Z_{eff}$ and inversely proportional to atomic size.  A stable electronic configuration requires more energy to remove an electron.
 2. Evaluate each option's contribution.
  Working: 
		* **A (Stable completely filled electronic configuration):** Inert gases have a completely filled valence shell ($ns^2np^6$), making them exceptionally stable. Removing an electron disrupts this stability, requiring significant energy.
		* **B (High effective nuclear charge):** Inert gases have a relatively high effective nuclear charge, meaning the valence electrons are strongly attracted to the nucleus, increasing ionization enthalpy.
		* **C (Small atomic size):**  Inert gases have small atomic sizes, leading to a stronger attraction between the nucleus and the valence electrons, thus higher ionization enthalpy.
		* **D (Presence of d-electrons in the valence shell):** Inert gases do *not* have d-electrons in their valence shell.  This option is incorrect and thus contributes LEAST to the high ionization enthalpy.
 3. Identify the least contributing factor.
  Result: The presence of d-electrons in the valence shell (option D) is irrelevant to inert gases, as they lack d-electrons in their valence shell.
  Verification: The other three factors (stable electronic configuration, high effective nuclear charge, and small atomic size) all directly contribute to the high ionization enthalpy of inert gases.
## OPTION ANALYSIS
A ✓: Stable completely filled electronic configuration contributes significantly to the high ionization enthalpy.
B :x: High effective nuclear charge significantly contributes to the high ionization enthalpy.
C :x: Small atomic size significantly contributes to the high ionization enthalpy.
D :x: Inert gases do not have d-electrons in their valence shell; this factor is irrelevant to their high ionization enthalpy.
## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing ionization enthalpy with electron affinity:  Electron affinity is the energy change when an electron is *added* to an atom, while ionization enthalpy involves *removing* an electron.
  2.Ignoring the role of effective nuclear charge:  The effective nuclear charge experienced by valence electrons is crucial in determining ionization enthalpy.
 **Quick Tips**:
  1.Remember the general periodic trends in ionization enthalpy: Ionization enthalpy generally increases across a period and decreases down a group.
  2.Relate ionization enthalpy to the stability of electronic configurations:  Atoms with stable electronic configurations have high ionization enthalpies.

Mr. S M HUSSAIN · Answer

Stable completely filled electronic configuration

Mr. S M HUSSAIN · Answer

High effective nuclear charge

Mr. S M HUSSAIN · Answer

Small atomic size

Mr. S M HUSSAIN · Answer

The correct Option is "Presence of d-electrons in the valence shell"

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