How many of the given species will behave as an electrophile?
`:C Cl_(2),NH_(3),overset(o+)(CH_(3)),overset(o+)(NH_(4)),overset(-)(CH_(3)),overset(-)(OH),BF_(3),AlCl_(3),overset(o+)(Br)`

Answer

To determine how many of the given species behave as electrophiles, we need to analyze each species based on its electron density and charge. Electrophiles are defined as electron-deficient species that can accept electrons from nucleophiles.

### Step-by-Step Solution:

1. **CCl₂ (Chlorocarbene)**:
- Chlorocarbene has two chlorine atoms attached to a carbon atom that has only 6 electrons in its valence shell (due to the two bonds with chlorine).
- **Conclusion**: CCl₂ is electron deficient and behaves as an electrophile.

2. **NH₃ (Ammonia)**:
- Ammonia has a lone pair of electrons on the nitrogen atom, making it electron-rich.
- **Conclusion**: NH₃ does not behave as an electrophile.

3. **CH₃⁺ (Methyl cation)**:
- The methyl cation has a positive charge and only 6 electrons around the carbon atom, indicating it is electron deficient.
- **Conclusion**: CH₃⁺ is an electrophile.

4. **NH₄⁺ (Ammonium ion)**:
- The ammonium ion has a complete octet with four hydrogen atoms bonded to nitrogen, making it stable and electron-rich.
- **Conclusion**: NH₄⁺ does not behave as an electrophile.

5. **CH₃⁻ (Methyl anion)**:
- The methyl anion has a negative charge and 8 electrons around the carbon atom, indicating it is electron-rich.
- **Conclusion**: CH₃⁻ does not behave as an electrophile.

6. **OH⁻ (Hydroxide ion)**:
- The hydroxide ion has a negative charge and a lone pair of electrons, making it electron-rich.
- **Conclusion**: OH⁻ does not behave as an electrophile.

7. **BF₃ (Boron trifluoride)**:
- Boron trifluoride has an incomplete octet (only 6 electrons), making it electron deficient and capable of accepting electrons.
- **Conclusion**: BF₃ is an electrophile.

8. **AlCl₃ (Aluminum chloride)**:
- Aluminum chloride also has an incomplete octet (only 6 electrons) and can accept electrons.
- **Conclusion**: AlCl₃ is an electrophile.

9. **Br⁺ (Bromonium ion)**:
- The bromonium ion has a positive charge, indicating it is electron deficient.
- **Conclusion**: Br⁺ is an electrophile.

### Summary of Electrophilic Species:
- Electrophiles: CCl₂, CH₃⁺, BF₃, AlCl₃, Br⁺
- Non-electrophiles: NH₃, NH₄⁺, CH₃⁻, OH⁻

### Total Count of Electrophiles:
There are **5 species** that behave as electrophiles.

---