(A) : In many crystal structures of ionic substances cations occupy the voids created by anions.
(R) : Cations are smaller than anions. 

Options

A. Both (A) and (R) are true. (R) properly explain (A)
B. Both (A) and (R) are true. (R) does not explain (A)
C. (A) is true. (R) is false
D. (A) is false. (R) is true

Answer

To solve the question, we need to analyze both the statement (A) and the reason (R) provided.

### Step 1: Understanding Statement (A)
The statement (A) says that in many crystal structures of ionic substances, cations occupy the voids created by anions.

- **Explanation**: In ionic compounds, anions (which are negatively charged) are typically larger than cations (which are positively charged). When these anions pack together in a crystal lattice, they create spaces or voids. These voids are the regions where smaller cations can fit.

### Step 2: Understanding Reason (R)
The reason (R) states that cations are smaller than anions.

- **Explanation**: This is a general characteristic of ionic compounds. Cations, being positively charged, have lost one or more electrons, resulting in a smaller radius compared to their neutral atoms. Anions, on the other hand, have gained electrons, leading to an increase in size. Therefore, cations are indeed smaller than anions.

### Step 3: Connecting (A) and (R)
Now, we need to connect the statement (A) with the reason (R).

- Since cations are smaller than anions, they can fit into the voids created by the larger anions. This supports the statement (A) that cations occupy the voids created by anions.

### Step 4: Conclusion
Both the statement (A) and the reason (R) are true, and the reason correctly explains the statement.

Thus, the correct answer is: **Both (A) and (R) are true and (R) is the correct explanation of (A)**.

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