| − | All atoms that contain the same number of protons.<ref>Wile, Dr. Jay L. ''Exploring Creation With Biology''. Apologia Educational Ministries, Inc. 1998</ref>
| + | An '''element''' is a single type of [[atom]] as defined by its [[atomic number]], which is the number of [[protons]] in its [[nucleus]].<ref>Wile, Dr. Jay L. ''Exploring Creation With Physical Science''. Apologia Educational Ministries, Inc. 1999, 2000</ref> In contrast, a single element may have varying [[mass number]]s, relating to the number of neutrons in its nucleus. |