Chemistry is the study of matter. All matter is made of atoms, which consist of protons, neutrons, and electrons that are identifiable by location, mass, and charge. These atoms make up the elements of the periodic table and elements within the same family on the periodic table have similar chemical properties because of similar atomic structure. An atoms electrons occupy various energy levels within the atom, each of which can hold a miximum number of electrons. The amount of electrons that can be held in these energy levels guides the formation of chemical bonds because atoms gain, share, or lose electrons to form chemical bonds and achieve stability. Ionic bonds result form the transfer of electrons where covalent bonds result from the sharing of electrons.