Explain why bond angle of `NH_(3)` is greater than `NF_(3)` while bond angle of `PH _(3)` is less than that of `PF _(3),`

Explanation

To explain why the bond angle of \( NH_3 \) is greater than \( NF_3 \) while the bond angle of \( PH_3 \) is less than that of \( PF_3 \), we can analyze the molecular structures and the effects of lone pairs and electronegativity on bond angles.

### Step-by-Step Solution:

1. **Identify the Central Atoms and Their Valence Electrons:**
- For \( NH_3 \) (Ammonia), nitrogen (N) has 5 valence electrons.
- For \( NF_3 \) (Nitrogen Trifluoride), nitrogen also has 5 valence electrons, but fluorine (F) has 7 valence electrons.
- For \( PH_3 \) (Phosphine), phosphorus (P) has 5 valence electrons.
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