Which one of the following statements is not correct ? (कौनस कथन सही नहीं है ?)

Options

A. All carbons is diamonds are linked by carbon-carbon ( single bond ( हीरे मे सभी कार्बन परमाणु एकल बंध के द्वारा जुड़े होते है )
B. Graphite is layered structure in which layers are held ( together by weak van der Walls forces.( ग्रेफ़ाइट की परतीय संरचना होती है जिनके बीच मे वाँडर वाल बल लगता है
C. Graphite layers are formed by hexagonal rings of carbon atoms
( ग्रेफ़ाइट मे षतकोणीय वलय होती है )
D. Graphite layers are held together by carbon-carbon single bond

Explanation

To determine which statement is not correct regarding the properties of carbon, particularly in its forms such as diamond and graphite, we can analyze each statement step by step.

### Step-by-Step Solution:

1. **Evaluate the First Statement:**
- **Statement:** "All carbon in diamonds are linked by carbon-carbon single bonds."
- **Analysis:** This statement is correct. In diamond, each carbon atom is tetrahedrally coordinated with four other carbon atoms through single covalent bonds, forming a three-dimensional network solid.

2. **Evaluate the Second Statement:**
- **Statement:** "Graphite is a layered structure in which layers are held together by weak van der Waals forces."
- **Analysis:** This statement is also correct. Graphite consists of layers of carbon atoms arranged in hexagonal rings, and these layers are held together by weak van der Waals forces, allowing them to slide over each other easily.

3. **Evaluate the Third Statement:**
- **Statement:** "Graphite layers are held together by carbon-carbon single bonds."
- **Analysis:** This statement is incorrect. The layers in graphite are not held together by carbon-carbon single bonds; instead, they are held together by weak van der Waals forces. Within each layer, the carbon atoms are bonded to each other through strong covalent bonds, but the layers themselves are not bonded by single bonds.

4. **Conclusion:**
- The statement that is not correct is the third one: "Graphite layers are held together by carbon-carbon single bonds."

### Final Answer:
The statement that is not correct is: "Graphite layers are held together by carbon-carbon single bonds."

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