Part 2: Fundamental Chemistry—Atoms

A single unit of an element is called an atom. At the center of an atom is a core called a nucleus that is composed of two types of subatomic particles: protons (positively charged particles) and neutrons (neutrally charged particles).  Atoms are considered electrically neutral because they also have negatively charged subatomic particles called electrons that circle around the atom’s nucleus. The charges of the protons and the electrons balance each other ensuring that the atom has no overall charge. Sometimes, an atom will gain or lose electrons, giving it an imbalanced number of protons and electrons. When this occurs, that atom has a charge and is called an ion.