| A | B |
|---|
| atom | smallest particle of matter that keeps the properties of matter |
| periodic table | organizational tool, arranged by increasing atomic number, shows patterns in the elements |
| isotope | atom with more or fewer neutrons than "normal" |
| proton | subatomic particle with a positive charge; found in the nucleus |
| electron | subatomic particle with a negative charge; found outside the nucleus in energy levels |
| neutron | subatomic particle with no charge; found in nucleus; helps hold nucleus of atom together |
| nucleus | where mass of the atom is located; center of atom; positive charge |
| energy levels | area around nucleus where electrons are found; now refer to as electron cloud |
| Democritus | first to come up with idea of atoms |
| Dalton | first to offer proof that atoms exist |
| Thomson | discovered electrons |
| Rutherford | found the nucleus with his gold foil experiment; said electrons were randomly scattered around nucleus |
| Bohr | modified Rutherford's model by putting electrons into energy levels |
| atomic number | how the periodic table is arranged; tells the number of protons in an atom |
| atomic mass | give the total number of protons and neutrons in the nucleus of an atom |
| atomic mass minus atomic number | tells the number of neutrons in an atom |
| energy level K; first level | can hold 2 electrons |
| energy level L; second level | can hold 8 electrons |
| energy level M; third level | can hold 18 electrons |
| neutral atom | atom where the number of protons is equal to the number of electrons |
