| A | B |
|---|
| Element | the simplest form of matter that has a unique set of properties and cannot be broken down into simpler substances by chemical means |
| Compound | a substance that contains two or more elements chemically combined in a fixed proportion |
| Atom | the smallest particle of an element that retains its identity in a chemical reaction |
| Atomic Mass | the weighted average of the masses of the isotopes of an element |
| Atomic Mass Unit (amu) | a unit of mass equal to one twelfth the mass of a carbon-12 atom |
| Atomic Number | the number of protons in the nucleus of an atom of an element |
| Electron | a negatively charged subatomic particle |
| Isotope | atoms of the same element that have the same atomic number but different atomic masses due to a different number of neutrons |
| Mass Number | the total number of protons and neutrons in the nucleus of an atom |
| Neutron | a subatomic particle with no charge and a mass of 1 amu; found in the nucleus of an atom |
| Proton | a positively charged subatomic particle found in the nucleus of an atom |
| Nucleus | the dense central portion of an atom |
