| Clue | Source | Date |
|---|---|---|
| Poisonous pale-yellow gas (8) | ||
| Strange iron fuel chemical (8) | ||
| Gas fitter's beginning in extension? | ||
| Gaseous element | The Times Concise | 24 Feb 2020 |
| Line four switched for nine on the periodic table | ||
| Four-line whips, highly toxic stuff | ||
| Element in Teflon | Newsday | 05 Jul 2018 |
| The "F" element in CFC | LA Times Daily | 27 Mar 2018 |
| The 'F' element in CFC | The Washington Post | 27 Mar 2018 |
| Teflon ingredient | ||
| Poisonous yellow gas | ||
| Most reactive element | ||
| Element #9 | ||
| Tooth-saving chemical. |