HYDROGEN

No 1 in the periodic table (8)

Solution has appeared in 4 crosswords (3 across and 1 down):

• Quick crossword No 16,645 — 2023-09-10 23:00:04
  7A: Most abundant chemical substance in the universe (8)
• Quick crossword No 16,500 — 2023-03-25 00:00:34
  13D: H (8)
• Quick crossword No 15,527 — 2020-02-12 00:00:17
  9A: Lightest gas (8)
• Quick crossword No 15,315 — 2019-06-07 23:00:40
  23A: No 1 in the periodic table (8)