To predict the molecular geometry of CH4, NH3, and H2O using the VSEPR theory, you need to follow these steps:
1. **Identify the central atom**: In CH4, the central atom is carbon; in NH3, it's nitrogen; and in H2O, it's oxygen.
2. **Count the total number of valence electrons**: Carbon has 4, nitrogen has 5, and oxygen has 6 valence electrons.
3. **Determine the number of bonding pairs**: In CH4, each hydrogen forms a single bond with carbon, so there are 4 bonding pairs. In NH3, each hydrogen forms a single bond with nitrogen, leaving 1 lone pair. In H2O, each hydrogen forms a single bond with oxygen, leaving 2 lone pairs.
4. **Apply VSEPR theory**:
- For CH4 (methane): With 4 bonding pairs and no lone pairs, the molecular geometry is tetrahedral.
- For NH3 (ammonia): With 3 bonding pairs and 1 lone pair, the molecular geometry is trigonal pyramidal.
- For H2O (water): With 2 bonding pairs and 2 lone pairs, the molecular geometry is bent/angular.
