The Question is from neet-chemistry the-solid-state structures-of-ionic-compounds, and it was created by the author A.RAMA NAGESWARARAO

Question

Which of the following statements regarding the radius ratio rule and its limitations is INCORRECT?

A.RAMA NAGESWARARAO · Accepted Answer

## CORE INFORMATION
✓ **Answer**: [C]
## CONCEPT FRAMEWORK
**Primary Concept**: Radius Ratio Rule
**Related Topics**: Ionic Crystal Structures, Coordination Number, Hard-Sphere Model
**Prerequisites**: Basic understanding of ionic compounds, crystal structures, and coordination numbers.
## SOLUTION PATHWAY
**Given Information**:
    * The question asks for the INCORRECT statement about the radius ratio rule.
**Method & Steps**:
    1.  Understand the radius ratio rule: The radius ratio rule predicts the coordination number of an ionic compound based on the ratio of the cation radius to the anion radius.
    2. Evaluate each statement:
        *   Option A is correct: It accurately describes the purpose of the radius ratio rule.
        *   Option B is correct: The radius ratio rule is based on the assumption of ions as hard spheres.
        *   Option C is incorrect: This is the statement we are looking for as the radius ratio rule is not perfect and has limitations.
        *   Option D is correct: Covalent character and crystal defects can cause deviations from predictions.
    3.  Identify the incorrect statement: Option C is the only incorrect statement.
**Result**: Option C is the incorrect statement.
## OPTION ANALYSIS
[A] :x:  This statement is correct and describes the general guideline provided by the radius ratio rule.
[B] :x: This statement is correct and highlights a major assumption of the radius ratio rule.
[C] ✓: This statement is incorrect. The radius ratio rule is a guideline and does not perfectly predict coordination numbers for all ionic compounds. Deviations occur due to factors like covalent bonding and crystal defects.
[D] :x: This statement is correct and explains some of the limitations of the radius ratio rule.
## LEARNING AIDS
**Common Mistakes**:
    1.  Assuming the radius ratio rule is always accurate: The rule is a guideline, not an absolute law.
    2.  Ignoring the limitations of the hard-sphere model: The hard-sphere model neglects polarization effects and covalent character.
**Quick Tips**:
    1.  Remember that the radius ratio rule is a useful tool, but it's not a perfect predictor due to the inherent simplifications.
    2.  Be aware that factors such as covalency and crystal defects can cause deviations from the predicted coordination numbers.

A.RAMA NAGESWARARAO · Answer

The radius ratio rule provides a general guideline for predicting the coordination number of an ionic compound based on the relative sizes of the cation and anion.

A.RAMA NAGESWARARAO · Answer

The radius ratio rule assumes a hard-sphere model for ions, neglecting polarization effects.

A.RAMA NAGESWARARAO · Answer

The correct Option is "The radius ratio rule perfectly predicts the coordination number for all ionic compounds, regardless of the size or charge of the ions involved."

A.RAMA NAGESWARARAO · Answer

Deviations from the predicted coordination number can occur due to covalent character in the bonding or the presence of defects in the crystal lattice.

NEET Chemistry The Solid State Structures Of Ionic Compounds MCQs

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