The chemical formula for ammonia is NH3. Which of the following models could be used to represent ammonia?

To represent ammonia (NH3), you could use several different models:

1. **Ball-and-Stick Model**: This model uses spheres (balls) to represent atoms (nitrogen and hydrogen) and sticks to represent the bonds between them. In the case of ammonia, you would have one larger sphere for nitrogen and three smaller spheres for the hydrogen atoms, with sticks connecting them. The geometry would show the trigonal pyramidal shape.

2. **Space-Filling Model**: This representation shows the relative sizes of the atoms and how they occupy space. In this model, the spheres representing nitrogen and hydrogen are sized according to their atomic radii and are placed to illustrate how they come together in ammonia.

3. **Lewis Structure**: A two-dimensional representation that shows the valence electrons as dots around the chemical symbols. The nitrogen atom would have three single bonds with the hydrogen atoms and one lone pair of electrons.

4. **Structural Formula**: This often conveys the bonding in a simpler way than Lewis structures, showing how the atoms are connected without all the details of lone pairs. For ammonia, a simple line diagram (N-H bonds shown with lines) could represent the connections.

Each of these models has its own advantages, and the choice of which to use would depend on the context in which ammonia is being discussed.