For an ionic crystan of the type `AB` , the value of (limiting) earius ratio is `0.40` .The value suggest that the crystan struture should be

Options

A. Octahedral
B. Tetrahedral
C. Square planar
D. Plane triangle

Answer

To determine the crystal structure of an ionic compound of type AB with a limiting radius ratio of 0.40, we can follow these steps:

### Step 1: Understand the Limiting Radius Ratio
The limiting radius ratio (r+/r-) is the ratio of the radius of the cation (r+) to the radius of the anion (r-). This ratio helps in predicting the geometry of the ionic crystal structure.

### Step 2: Identify the Given Value
In this case, the limiting radius ratio is given as 0.40.

### Step 3: Refer to the Radius Ratio Table
According to the radius ratio table for ionic crystals:
- If the radius ratio (r+/r-) is between 0.155 and 0.225, the structure is triangular (or planar).
- If the radius ratio (r+/r-) is between 0.225 and 0.414, the structure is tetrahedral.
- If the radius ratio (r+/r-) is greater than 0.414, the structure is octahedral.

### Step 4: Analyze the Given Ratio
Since the given limiting radius ratio is 0.40, we can see that it falls within the range of 0.225 to 0.414.

### Step 5: Conclude the Crystal Structure
Since the limiting radius ratio of 0.40 is between 0.225 and 0.414, we conclude that the crystal structure of the ionic compound AB will be tetrahedral.

### Final Answer
The crystal structure should be tetrahedral.

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