| A | B |
|---|
| atom | particle that cannot be cut |
| electron | negatively charged particle discovered by Thomson |
| nucleus | central region of the atom |
| electron cloud | region where elelectrons are likely to be found |
| neutron | particle in the center of an atom that has no charge |
| protron | subatomic particle that has a postive charge |
| atomic mass unit (amu) | a unit of mass that describes the mass of an atom or molecule |
| atomic number | number of protons in the nucleus of an atom |
| isotope | atom that has the same number of protons but different numbers of neutrons |
| mass number | sum of protons and neutrons in an atom |
