| A | B |
|---|
| wavelength | distance between two waves |
| frequency | the number of waves that pass a given point per unit of time |
| photon | tiny packet of energy |
| excited state | contains an electron with excess energy |
| ground state | lowest possible energy state for an atom |
| orbital | region where an electron resides in an atom |
| Pauli Exclusion Principle | an atomic orbital can hold no more than two electrons, and they must be of opposite spin |
| valence electrons | electrons in outermost (highest) occupied principal energy level |
| core electrons | inner electrons |
| ionization energy | energy required to remove an electron from an atom in the gas phase |
