Final answer:
Ammonia (NH3) and water (H2O) are examples involving determining the number of electron domains.
Step-by-step explanation:
An example involving determining the number of electron domains is ammonia (NH3). In this molecule, nitrogen is the central atom and has three peripheral atoms at the corners of a triangle, resulting in a trigonal pyramidal electron domain geometry. The bond angle in ammonia is approximately 107 degrees. Another example is water (H2O), where oxygen is the central atom and the molecule has two electron domains - two bonding pairs or lone pairs. This results in a bent molecular geometry with a bond angle of approximately 104.5 degrees.