| A | B |
|---|
| Name | Definition |
| period | a horizontal row of elements on the periodic table |
| group | vertical column of elements on the periodic table |
| metallic | the collective properties of common metals |
| luster | shine; a property of metals |
| conductivity | ability of a material to transfer electricity or thermal energy (heat) |
| halogens | elements in Group 17 – most reactive nonmetals |
| noble gas | elements in Group 18 -extremely stable by themselves |
| element | pure substance made from atoms that all have the same number of protons |
| radioactive decay | occurs when an unstable atomic nucleus changes into another nucleus by emitting one or more particles and energy |
| radioactive | a nucleus that is unstable and undergoes radioactive decay |
| transmutation | an atom of one element is changed into an atom of another element through radioactive decay |
| radioactive elements | elements having only radioactive isotopes |
| half-life | the time it takes for a sample of radioactive isotope to decay to half its original mass |
| synthetic elements | radioactive elements that are made by scientists in laboratories or created during nuclear reactions |
| particle accelerator | a large machine that is capable of making particles move very fast |
| isotope | one of two or more atoms of an element having the same number of protons in their nuclei, but a different number of neutrons |
| physical property | any characteristic of a material that can be observed without changing the identity of the material itself |
| melting point | temperature at which a solid changes to a liquid |
| boiling point | temperature at which a liquid changes to a gas |
| thermal conductivity | ability of a material to transfer heat by collisions between its particles |
| electrical conductivity | the ability of a material to transfer electric charges through a material |
| physical change | any change in the size, shape, or the state of matter in which the identity of the substance is unchanged |
| density | the mass of an object divided by its volume |
