Atoms Chapter 1 Review Tools A B compound a combination of two or more elements electrons, protons, and neutron 3 basic parts of an atom electron cloud where the electron is found mass number add the number of protons plus neutrons isotopes atom with same number of protons, but different number of neutrons salad example of a heterogenous mixture atomic number equal to the number of protons in an atom metals make up most of the periodic table protons positive charge; counted to identify the atomic number electron smallest part of an atom nonmetals found on the right side of the periodic table neutron no charge; about the same mass as a proton electron cloud region surrounding the nucleus in which the electrons move about metalloids elements that have characteristics of both metals and nonmetals compound water is an example of a ____ neutron found in the nucleus; no charge element contains only one kind of atom nucleus where protons and neutrons are found