Match the following terms and definitions. 1. the smallest unit of an element atomic mass 2. the path surrounding the nucleus of an atom in which electrons are normally located electron 3. the number of protons in the nucleus of the atom compound 4. a pure substance where atoms of two or more elements are chemically bonded to one another neutron 5. the positively charged center of an atom atom 6. exists in orbit around the nucleus of an atom and carries a negative charge molecule 7. the smallest unit of a pure substance that consists of two or more atoms held together by a chemical bond shell 8. the mass of an element diatomic 9. a subatomic particle that carries no charge atomic number 10. containing two atoms nucleus 11. a subatomic particle with a positive charge proton