| A | B |
|---|
| Atom | smallest unit of an element that maintains the properties of that element |
| electron | subatomic particle with a negative charge |
| nucleus | refers to the atom's central region comprised of protons and neutrons |
| electron cloud | a region around the nucleus of an atom where electrons are likely to be found |
| proton | a subatomic particle that has a positive charge and is located inside the nucleus |
| atomic mass unit | a unit of mass that describes the mass of an atom or molecule |
| neutron | a subatomic particle that has no charge and is located inside the nucleus |
| atomic number | the number of protons inside the nucleus of an atom |
| isotope | an atom that has the same number of protons and electrons as other atoms of that element, but these have different numbers of neutrons |
| mass number | the sum of the protons and neutrons in the nucleus of an atom |
| atomic mass | the mass of an atom expressed in atomic mass units |
