How many among the following species can be classified as Lewis acids?
`overset(o+)(CH_(3)), Cl^(o+),CO_(2), "CCl"_(2), BCl_(3), BI_(3), Fe^(+2), AlCl_(3)`

Answer

To determine how many of the given species can be classified as Lewis acids, we need to analyze each species based on the definition of a Lewis acid. A Lewis acid is defined as a substance that can accept a pair of electrons to form a covalent bond.

Let's evaluate each species one by one:

1. **CH₃⁺ (methyl cation)**:
- The carbon atom in CH₃⁺ has a positive charge, indicating it has an empty p-orbital available to accept a lone pair of electrons.
- **Conclusion**: CH₃⁺ is a Lewis acid.

2. **Cl⁺ (chloronium ion)**:
- The chlorine atom in Cl⁺ also has a positive charge, which means it can accept electrons. Chlorine can utilize its empty p-orbitals for this purpose.
- **Conclusion**: Cl⁺ is a Lewis acid.

3. **CO₂ (carbon dioxide)**:
- CO₂ is a linear molecule with a central carbon atom that can accept electron pairs from nucleophiles. The carbon atom has vacant p-orbitals available for bonding.
- **Conclusion**: CO₂ is a Lewis acid.

4. **CCl₂ (dichlorocarbene)**:
- CCl₂ has a carbon atom with one vacant p-orbital, which can accept a lone pair of electrons.
- **Conclusion**: CCl₂ is a Lewis acid.

5. **BCl₃ (boron trichloride)**:
- Boron in BCl₃ has an incomplete octet and can accept a pair of electrons to complete its octet. It has empty p-orbitals available for this purpose.
- **Conclusion**: BCl₃ is a Lewis acid.

6. **BiI₃ (bismuth triiodide)**:
- Similar to BCl₃, BiI₃ has a central bismuth atom that can accept electron pairs due to its empty p-orbitals.
- **Conclusion**: BiI₃ is a Lewis acid.

7. **Fe²⁺ (ferrous ion)**:
- The Fe²⁺ ion has vacant orbitals (specifically in the 3d subshell) that can accept electrons.
- **Conclusion**: Fe²⁺ is a Lewis acid.

8. **AlCl₃ (aluminum chloride)**:
- Aluminum in AlCl₃ also has an incomplete octet and can accept electron pairs, having empty p-orbitals available for bonding.
- **Conclusion**: AlCl₃ is a Lewis acid.

After evaluating all the species, we find that all of them can be classified as Lewis acids.

**Final Answer**: There are **8** Lewis acids among the given species.