| A | B |
|---|
| Periods | Rows, across |
| Groups/Families | Columns, down |
| Atomic Number | Tells you # protons and # electrons |
| Atomic Mass/Weight | Tells you # of protons + neutrons |
| How to find number of neutrons | subtract! atomic mass - atomic number |
| Charge of Protons | positive |
| Charge of Electrons | negative |
| Charge of Neutrons | Neutral |
| Where are protons in an atom? | in the nucleus |
| Where are neutrons in an atom? | in the nucleus |
| Where are electrons in an atom? | outside the nucleus in energy levels or "shells" or "orbits" |
| Number of electrons the first 3 energy levels can hold | up to 2, then up to 8, then up to 8 |
| Elements in the same group have the same | number of valence electrons |
| Electrons in the outermost energy level | valence electrons |
