To determine the number of molecules with a pyramidal shape from the given list, we need to analyze each molecule based on its hybridization and steric number. A pyramidal shape typically corresponds to a steric number of 4, which means there are 3 bond pairs and 1 lone pair of electrons.
Let's analyze each molecule step by step:
1. **NH₃ (Ammonia)**:
- Nitrogen has 5 valence electrons.
- It forms 3 bonds with hydrogen atoms, using 3 of its electrons.
- This leaves 2 electrons, which form 1 lone pair.
- Therefore, the steric number = 3 (bond pairs) + 1 (lone pair) = 4.
- **Hybridization**: sp³.
- **Shape**: Pyramidal.
2. **ClF₃ (Chlorine Trifluoride)**:
- Chlorine has 7 valence electrons.
- It forms 3 bonds with fluorine atoms, using 3 of its electrons.
- This leaves 4 electrons, which form 2 lone pairs.
- Therefore, the steric number = 3 (bond pairs) + 2 (lone pairs) = 5.
- **Hybridization**: sp³d.
- **Shape**: Not pyramidal.
3. **SO₃ (Sulfur Trioxide)**:
- Sulfur has 6 valence electrons.
- It forms 3 double bonds with oxygen atoms, using all 6 electrons.
- Therefore, the steric number = 3 (bond pairs) + 0 (lone pairs) = 3.
- **Hybridization**: sp².
- **Shape**: Not pyramidal.
4. **PCl₃ (Phosphorus Trichloride)**:
- Phosphorus has 5 valence electrons.
- It forms 3 bonds with chlorine atoms, using 3 of its electrons.
- This leaves 2 electrons, which form 1 lone pair.
- Therefore, the steric number = 3 (bond pairs) + 1 (lone pair) = 4.
- **Hybridization**: sp³.
- **Shape**: Pyramidal.
5. **XeO₃ (Xenon Trioxide)**:
- Xenon has 8 valence electrons.
- It forms 3 bonds with oxygen atoms, using 6 electrons.
- This leaves 2 electrons, which form 1 lone pair.
- Therefore, the steric number = 3 (bond pairs) + 1 (lone pair) = 4.
- **Hybridization**: sp³.
- **Shape**: Pyramidal.
6. **BCl₃ (Boron Trichloride)**:
- Boron has 3 valence electrons.
- It forms 3 bonds with chlorine atoms, using all 3 electrons.
- Therefore, the steric number = 3 (bond pairs) + 0 (lone pairs) = 3.
- **Hybridization**: sp².
- **Shape**: Not pyramidal.
7. **ClO₃⁻ (Chlorate Ion)**:
- Chlorine has 7 valence electrons.
- It forms 3 bonds with oxygen atoms, using 3 electrons.
- The negative charge adds 1 more electron, making it 8 total.
- Therefore, the steric number = 3 (bond pairs) + 1 (lone pair) = 4.
- **Hybridization**: sp³.
- **Shape**: Pyramidal.
8. **SO₃²⁻ (Sulfite Ion)**:
- Sulfur has 6 valence electrons.
- It forms 3 bonds with oxygen atoms, using 3 electrons.
- The negative charge adds 2 more electrons, making it 8 total.
- Therefore, the steric number = 3 (bond pairs) + 1 (lone pair) = 4.
- **Hybridization**: sp³.
- **Shape**: Pyramidal.
Now, let's count the molecules that have a pyramidal shape:
- NH₃: Pyramidal
- PCl₃: Pyramidal
- XeO₃: Pyramidal
- ClO₃⁻: Pyramidal
- SO₃²⁻: Pyramidal
**Total number of molecules with pyramidal shape = 5.**
### Final Answer:
The number of molecules with a pyramidal shape is **5**.
