| A | B |
|---|
| atom | the basic building block of matter. |
| electrons | negatively charged particles |
| nucleus | a positively charged center of an atom |
| protons | positively charged particles |
| neutrons | particles with no charge |
| electron cloud | a model of an atom based on the electron's most probable location |
| atomic number | the number of protons |
| Bohr model | a model of an atom in which eletrons move in well defined orbits around a nucleus |
| energy level | different amounts of energy that electrons can have |
| Quark | smaller particles that make up protons and neutrons |
