| A | B |
|---|
| matter that is made up of only one kind of atom | element |
| a negatively charged particle that is part of the atom | electron |
| a positively charged particle that is present in the nucleus of all atoms | proton |
| uncharged particle in the nucleus of an atom | neutron |
| region surrounding the nucleus in which the electrons move about | electron cloud |
| the number of protons in the nucleus of an atom of an element | atomic number |
| atoms of an element that differ in the number of neutrons | isotopes |
| the number of neutrons plus protons in the nucleus of an atom | mass number |
