| alkali metals | Silvery solids with low densities and low melting points found in Group 1 |
| alloy | A mixture of two or more elements,one of which is a metal |
| ductile | , Capable of being drawn out, as into wire or a thread. |
| atomic number | Basis for arranging elements in modern periodic table |
| actinides | Radioactive, unstable elements in transition metals |
| group | A vertical row of elements in the periodic table, elements in group share chemical properties, also called a family |
| halogens | Group of elements that form salt |
| hydrogen | Only nonmetal in group 1 |
| lanthanides | Series of elements that are sometimes called rare earth elements |
| malleable | Capable of being shaped or bent or drawn out |
| metals | They are shiny, ductile, malleable, good conductors of thermal energy |
| metalloids | Have characteristics of both metals and nonmetals |
| noble gases | These elements do NOT react with any other elements. |
| nonmetals | Not malleable, not ductile, not shiny, poor conductors of thermal energy and electric current, |
| periods | Horizontal rows of periodic table; within period, elements near each other have similar properties |
| mass number | The total number of protons and neutrons in an atom's nucleus |
| representative elements | A group in the periodic table which includes metals, metalloids, and nonmetals |
| semiconductors | Elements that show moderate electrical conductivity |
| transition elements | Elements in Groups 3-12 of the periodic table |