In which of the following pairs both the solids belong to same type ?

Options

A. SiC, AlN
B. `CaF_2, Ca`
C. Graphite , Ice
D. Solid `CO_2` , ZnS

Answer

To determine which pair of solids belongs to the same type, we need to analyze the bonding and characteristics of each solid in the given options.

### Step-by-Step Solution:

1. **Identify the First Pair: SiC and AlN**
- **SiC (Silicon Carbide)**: This is a covalent solid. It consists of covalent bonds between silicon and carbon atoms. Covalent solids typically have very high melting points due to the strong bonding.
- **AlN (Aluminum Nitride)**: This is also a covalent solid. It consists of covalent bonds between aluminum and nitrogen atoms. Similar to SiC, AlN has a high melting point.
- **Conclusion**: Both SiC and AlN are covalent solids.

2. **Identify the Second Pair: CaF2 and Ca**
- **CaF2 (Calcium Fluoride)**: This is an ionic solid. It consists of electrostatic forces between calcium ions (Ca²⁺) and fluoride ions (F⁻). Ionic solids also have high melting points.
- **Ca (Calcium)**: This is a metallic solid. It consists of metallic bonding, which involves a sea of delocalized electrons. Metallic solids also have high melting points but are fundamentally different in bonding.
- **Conclusion**: CaF2 is ionic, while Ca is metallic. They are different types of solids.

3. **Identify the Third Pair: Graphite and Ice**
- **Graphite**: This is a covalent solid. It consists of layers of carbon atoms bonded covalently, with weak van der Waals forces between layers. It has a high melting point.
- **Ice**: This is a molecular solid. It consists of water molecules held together by hydrogen bonds, which are relatively weaker than covalent bonds. Ice has a low melting point compared to graphite.
- **Conclusion**: Graphite is covalent, while ice is a molecular solid. They are different types of solids.

4. **Identify the Fourth Pair: Solid CO2 and ZnS**
- **Solid CO2 (Dry Ice)**: This is a molecular solid. It consists of carbon dioxide molecules held together by London dispersion forces. It has a low melting point.
- **ZnS (Zinc Sulfide)**: This is an ionic solid. It consists of zinc ions (Zn²⁺) and sulfide ions (S²⁻) held together by strong electrostatic forces. ZnS has a high melting point.
- **Conclusion**: Solid CO2 is molecular, while ZnS is ionic. They are different types of solids.

### Final Conclusion:
The only pair where both solids belong to the same type is **Option 1: SiC and AlN**, as both are covalent solids.