| A | B |
| isotope | a version of an atom with a different number of neutrons |
| metal | a substance that is shiny, malleable, and a good conductor |
| noble gases | a group in the PTE containing non-reactive elements |
| halogens | a group in the PTE containing very reactive non-metals |
| element | a type of atom with a unique number of protons |
| atomic number | the number of protons of an atom |
| atomic mass | the number of protons + neutrons of an atom |
| malleable | can be bent instead of broken |