Three centred two electron bond is present in

Options

A. `NH_(3)`
B. `B_(2)H_(6)`
C. `BCl_(3)`
D. `AlCl_(3)`

Answer

To determine which compound has a three-centered two-electron bond, we will analyze each of the given compounds: NH3, B2H6, BCl3, and AlCl3.

### Step-by-Step Solution:

1. **Understanding Three-Centered Two-Electron Bonds**:
- A three-centered two-electron bond, often referred to as a "banana bond," involves three atomic centers sharing two electrons. This type of bonding is typically found in certain boron compounds.

2. **Analyzing NH3 (Ammonia)**:
- NH3 has a trigonal pyramidal structure due to the presence of a lone pair on nitrogen.
- In NH3, the bonding involves two electrons shared between nitrogen and three hydrogen atoms, but there are no three-centered bonds.
- **Conclusion**: NH3 does not have a three-centered two-electron bond.

3. **Analyzing B2H6 (Diborane)**:
- B2H6 has a unique structure where two boron atoms are connected by hydrogen atoms.
- In diborane, there are two three-centered two-electron bonds (banana bonds). Each bond involves two boron atoms and one hydrogen atom.
- **Conclusion**: B2H6 contains three-centered two-electron bonds.

4. **Analyzing BCl3 (Boron Trichloride)**:
- BCl3 has a trigonal planar structure with boron at the center and three chlorine atoms surrounding it.
- There are no three-centered two-electron bonds in BCl3 as all bonds are typical two-centered bonds.
- **Conclusion**: BCl3 does not have a three-centered two-electron bond.

5. **Analyzing AlCl3 (Aluminum Chloride)**:
- AlCl3 also has a trigonal planar structure similar to BCl3.
- Like BCl3, AlCl3 does not exhibit any three-centered two-electron bonds; it has standard two-centered bonds between aluminum and chlorine.
- **Conclusion**: AlCl3 does not have a three-centered two-electron bond.

6. **Final Conclusion**:
- Among the compounds analyzed, only B2H6 contains a three-centered two-electron bond.

### Answer:
The three-centered two-electron bond is present in **B2H6** (Diborane).