| Clue | Source | Date |
|---|---|---|
| Radioactive chemical element; symbol Fr (8) | Mirror Quiz | 28 Dec 2025 |
| Radioactive element with the symbol Fr | The Times Specialist | 17 Nov 2025 |
| Radioactive chemical element with the atomic number 87 (8) | ||
| Unstable element | The Times Concise | 21 Sep 2021 |