| 2025-09-13 | Chemistry class unit: Abbr. |
| 2020-04-25 | Unit in chemistry: Abbr. |
| 2019-02-24 | Chemistry unit: Abbr. |
| 2018-05-06 | Kind of biol. |
| 2018-03-03 | Chem. unit |
| 2017-06-29 | Chem. unit |
| 2015-06-14 | Chemistry unit: Abbr. |
| 2015-01-21 | Chem. unit |
| 2014-10-19 | Group of atoms: Abbr. |
| 2012-01-30 | Collection of atoms: Abbr. |
| 2011-11-06 | Chem. unit |
| 2010-12-18 | CO, e.g.: Abbr. |
| 2007-10-28 | Chem. unit |
| 2006-04-07 | 40-Down, e.g.: Abbr. |
| 2006-03-08 | Small matter: Abbr. |
| 2005-10-23 | Small particle: Abbr. |
| 2005-03-13 | Unit of matter: Abbr. |
| 2003-10-03 | Collection of atoms: Abbr. |
| 2003-06-27 | Chem. unit |
| 2002-11-02 | Elem. unit |
| 1999-11-14 | Tiny particle: Abbr. |
| 1999-04-18 | Group of atoms: Abbr. |
| 1996-06-02 | Elem. particle |