The radius ratio `(r_(+)//r_(-))` of an ionic solid `(A^(+)B^(-))` is 0.69. What is the coordination number of `B^(-)`

Options

A. 6
B. 8
C. 2
D. 10

Explanation

To determine the coordination number of \( B^{-} \) in the ionic solid \( A^{+}B^{-} \) given the radius ratio \( \frac{r_{+}}{r_{-}} = 0.69 \), we can follow these steps:

### Step 1: Understand the Radius Ratio Concept
The radius ratio \( \frac{r_{+}}{r_{-}} \) is a crucial factor in determining the coordination number in ionic compounds. The radius of the cation (\( r_{+} \)) is compared to the radius of the anion (\( r_{-} \)).

### Step 2: Identify the Range for Coordination Numbers
Based on the radius ratio, we can classify the coordination number according to the following ranges:
- \( 0.155 < \frac{r_{+}}{r_{-}} < 0.225 \): Coordination number = 3 (triangular)
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