Which of the following statements is incorrect ?

Options

A. In `K_(3)[Fe(CN)_(6)]` the ligand has satisfied only the secondary valency of ferric ion .
B. In `K_(3)[Fe(CN)_(6)`, the ligand has satisfied both primary and secondary valencies of ferric ion
C. In `K_(4)[Fe(CN)_(6)]` the ligand has satisfied both primary and secondary valencies of ferrous ion.
D. In `[Cu(NH_(3))_(4)]SO_(4)` the ligand has satisfied only the secondary valency of copper.

Explanation

To determine which statement is incorrect regarding coordination compounds, we will analyze each statement based on the principles of Werner's theory, which describes the valencies of metal ions in coordination complexes.

### Step-by-Step Solution:

1. **Understanding Primary and Secondary Valency**:
- According to Werner's theory, primary valency refers to the oxidation state of the metal ion, while secondary valency corresponds to the coordination number, which is the number of ligands attached to the central metal atom.

2. **Analyzing the Statements**:
- **Statement 1**: In potassium hexacyanoferrate, the ligand has satisfied only the secondary valency of the ferric ion.
- **Analysis**: The cyanide ligands (CN⁻) in potassium hexacyanoferrate satisfy both the primary and secondary valencies of the ferric ion (Fe³⁺). The primary valency is satisfied by the negative charge of the cyanide ligands. Therefore, this statement is incorrect.

- **Statement 2**: The primary valency is satisfied only by negative ions.
- **Analysis**: This statement is correct. Primary valency is indeed satisfied by negative ions (anions).

- **Statement 3**: The secondary valency is satisfied by negative ions and neutral molecules.
- **Analysis**: This statement is also correct. Secondary valency can be satisfied by both anions and neutral ligands.

3. **Conclusion**:
- The incorrect statement is **Statement 1**. It misrepresents the role of ligands in satisfying the primary valency of the metal ion.

### Final Answer:
The incorrect statement is **Statement 1**: In potassium hexacyanoferrate, the ligand has satisfied only the secondary valency of the ferric ion.

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