| Question | Answer |
|---|---|
| region at the center of an atom that contains most of the mass of an atom | nucleus |
| an atom that has a charge because it has gained or lost electrons | ion |
| the modern model of an atom is called the______model | electron-cloud |
| Isotopes have the same number of protons but different numbers of________ | neutrons |
| which particle in an atom has a positive charge | proton |
