Which of the following statement is/are incorrect in the rock-salt structure if an ionic compounds ? (A) coordination number of cation is four where as that of anion is six.
(B) coordination number of cation is six where as that of anion is four.
(C) coordination number of each cation and anion is four.
(D) coordination number of each cation and anion is six.

Explanation

To determine which statements regarding the rock-salt structure of ionic compounds are incorrect, we need to analyze the coordination numbers of the cations and anions in this structure.

### Step-by-Step Solution:

1. **Understanding Rock-Salt Structure**:
- The rock-salt structure is a common crystal structure for ionic compounds, exemplified by sodium chloride (NaCl).
- In this structure, cations (Na⁺) and anions (Cl⁻) are arranged in a cubic lattice.

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