| A | B |
|---|
| periodic table | an arrangement of the elements by increasing atomic number |
| nucleus | the dense, positively charged core of an atom |
| radioactive element | an element that naturally breaks down into a less massive element, giving off rays of enery and streams of particles. |
| proton | positively charged particle in the nucleus of an atom. |
| chemical change | change that forms new substances with new properties. |
| isotope | one of a group of atoms of an element with the same number of protons but different numbers of neutrons. |
| quark | one of two basic building blocks of an atom. |
| neutral | having no charge. |
| chemical property | characteristic that determines how a substance reacts with other substances. |
| physical change | change that does not affect the composition of a substance. |
| physical property | characteristic that can be observed without changing the composition of a substance. |
| atomic number | number of protons in an atom of an element. |
| mass number | the total number of protons and neutrons in the nucleus of an atom. |
| electron | a tiny, negatively charged particle outside the nucleus of an atom. |
| chemical bond | strong attraction between two atoms. |
| neutron | uncharged particle in the nucleus of an atom. |
