| A | B |
|---|
| Democritus | Ancient Greek who proposed the atom |
| Atom | The smallest particle into which an element can be divided and still be the same substance |
| Solid Sphere model | 1st model of atom (Dalton) |
| Plum Pudding model | 2nd model of atom (Thomson) |
| Rutherford model | 3rd model of atom (with nucleus) |
| Bohr model | 4th model of atom (with orbits) |
| Electron Cloud model | Current model of atom |
| Proton | Positive particle, in nucleus |
| Neutron | Neutral particle, in nucleus |
| Electron | Negative particle, outside nucleus |
| Quarks | Extremely tiny particles that make up protons and neutrons |
| Atomic Number | The number of protons in an atom’s nucleus |
| Isotopes | Atoms of the same element that have different numbers of neutrons |
| Mass Number | The sum of the number of protons and neutrons in an atom |
| Average atomic mass | The weighted average mass of all naturally occurring isotopes of an element |
| First energy level | Energy level that can hold 2 electrons |
| Second energy level | Energy level that can hold 8 electrons |
| Third energy level | Energy level that can hold 18 electrons |
| Periodic Table | An arrangement of the elements by increasing atomic number and by changes in chemical and physical properties |
| Mendeleev | Created first useful periodic table |
| Periods | The rows on the periodic table |
| Groups | The columns on the periodic table |
| Metals | Elements to the left of the Zig Zag |
| Nonmetals | Elements to the right of the Zig Zag |
| Metalloids | Elements on the Zig Zag |
