| A | B |
|---|
| nucleus | positively charged center of the atom |
| proton | positively charged particle inthe nucleus |
| neutron | uncharged particle in the nucleus |
| electron | negatively charged particle |
| electron cloud | area surrounding nucleus in which electrons are found |
| Thomson | discovered the electron |
| Rutherford | described the positive nucleus |
| Bohr | assigned electrons to specific orbits |
| Dalton | formulated the atomic theory |
| Democritus | Greek who first coined term "atom" |
| strong force | holds protons inthe nucleus |
| weak force | responsible for radioactive decaywithin the nucleus |
| gravity | force of attraction between all objects |
| electromagnetic force | keeps the electrons in orbit around the nucleus |
| quark | subatomic particle that makes up protons and neutrons |
| period | horizontal row on periodic table |
| family | vertical column on periodic table |
| Mendeleev | designed periodic table |
| atomic mass | used by Mendeleev to put elements in order |
| atomic number | used today to put elements in order |
| noble gases | do not combine with other elements |
| metals | elements that give up electrons |
| nonmetals | elements that take electrons |
| metalloids | elements with characteristics of both metals and nonmetals |
