| A | B |
|---|
| element | A material that cannot be broken down into simpler materials by ordinary means. |
| Period table of the elements | A chart created by chemists to help organize and display the elements. |
| Atomic number | Number of protons in the nucleus of an atom. |
| Atomic mass | How heavy an atom is compared with atoms of other elements. |
| Isotopes | Atoms of the same element that have different numbers of neutrons. |
| Mass number | The sum of an atom's protons and neutrons. |
| Metals | Elements that are shiny, good conductors, and malleable |
| Nonmetals | elements that are usually dull, poor conductors, and brittle |
| metalloids | elements with characteristics of metals and nonmetals. |
