Do `NH_(3)` and `BF_(3)` have same shape ?

Answer

To determine if \( NH_3 \) (ammonia) and \( BF_3 \) (boron trifluoride) have the same shape, we can analyze their molecular structures based on their valence electrons and bonding.

### Step-by-Step Solution:

1. **Identify the Valence Electrons:**
- For \( NH_3 \): Nitrogen (N) has 5 valence electrons (configuration: \( 1s^2 2s^2 2p^3 \)). Each hydrogen (H) has 1 valence electron. Thus, the total number of valence electrons in \( NH_3 \) is \( 5 + 3(1) = 8 \).
- For \( BF_3 \): Boron (B) has 3 valence electrons (configuration: \( 1s^2 2s^2 2p^1 \)). Each fluorine (F) has 7 valence electrons. Thus, the total number of valence electrons in \( BF_3 \) is \( 3 + 3(7) = 24 \).

2. **Determine the Bonding Pairs and Lone Pairs:**
- In \( NH_3 \): Nitrogen forms three bonds with hydrogen atoms, using 3 of its valence electrons. This leaves 1 lone pair of electrons on the nitrogen atom.
- In \( BF_3 \): Boron forms three bonds with fluorine atoms, using all of its valence electrons. There are no lone pairs on the boron atom.

3. **Determine the Molecular Geometry:**
- For \( NH_3 \): The presence of one lone pair and three bond pairs leads to a trigonal pyramidal shape. The lone pair pushes the hydrogen atoms down, creating a pyramid shape.
- For \( BF_3 \): With no lone pairs and three bond pairs, the shape is trigonal planar. The three fluorine atoms are arranged in a flat plane around the boron atom.

4. **Conclusion:**
- Since \( NH_3 \) has a trigonal pyramidal shape and \( BF_3 \) has a trigonal planar shape, they do not have the same shape.

### Final Answer:
No, \( NH_3 \) and \( BF_3 \) do not have the same shape. \( NH_3 \) is trigonal pyramidal, while \( BF_3 \) is trigonal planar.

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