An atom is an example of a system, or a group of objects that interact with each other. Scientists often use a model to represent a system that is hard to see. Models can also be used to show a complicated system in a simpler way. Because atoms are so hard to see, people use atomic models to represent the way protons, neutrons, and electrons are arranged in an atom. The diagram below is an example of an atomic model. In this model, a positive electrical charge is shown with the plus symbol (+) and a negative electrical charge is shown with the minus symbol (–). Use the words below to label each part of the model. a)electron b)proton c)atoms d)neutron