| A | B |
|---|
| Nucleus | Center of the atom; contains protons and neutrons |
| Protons | Positively charged subatomic particles |
| Neutrons | Subatomic particles with no charge |
| Electrons | Negatively charged subatomic particles |
| Orbitals | Region of an atom where an electrons might be found |
| Periodic Law | Chemical and physical properties repeat when elements are arranged by atomic number |
| Period | Horizantal rows of the periodic table |
| Group (Family) | Vertical columns of the period table |
| Ion | A positively or negatively charge atom or groups of atoms |
| Atomic Number | Equals the number of protons in an atom |
| Mass Number | Equals the number of protons and neutrons in an atom |
| Isotopes | Atoms that have a different number of neutrons than typical atoms in the element |
| Atomic Mass Unit | Unit of mass that describes the mass of an atom or molecule |
| Average Atomic Mass | Average mass of all the isotopes of an element |
