| A | B |
|---|
| atomic number | # or protons |
| mass number | # protons + neutrons |
| protons | positively charged nuclear particle |
| electrons | negatively charged particle in energy levels around nucleus |
| neutrons | neutral nuclear particle |
| ion | charged atom |
| isotope | atom with a different number of neutrons & mass number |
| nucleus | positively charged, massive dense center of an atom |
| charge | # protons - # electrons |
| atomic mass | weighted average of all isotopes of an element |
| Rutherford | discovered the nucleus (gold foil exp.) |
| Bohr | said electrons are in energy levels around nucleus |
| energy levels | where electrons are found |
| Dalton | said atoms were solid & indivisible, developed the first atomic theory |
| Thomson | discovered the electron (cathode ray tube) |
| Aufbau Principle | says e- fill lowest energy levels first |
| Pauli Exclusion Principle | only 2 e- in the same orbital, with opposite spins |
| Hunds Rule | if orbitals have equal energy, electrons will go into each orbital before any orbital gets filled |
| sub levels | s, p, d, or f |
| atom | the basic unit of matter |
| Quantum Mechanical Model | describes in detail the movement of electrons in the energy levels, newest model |
| s sublevel | only 1 orbital, 2 electrons max |
| p sublevel | 3 equal orbitals, 6 electrons max |
| d sublevel | 5 orbitals, 10 electrons max |
| f sublevel | 7 orbitals, 14 electrons max |
