How many letters does the top answer for “any of a series of radioactive elements with atomic numbers 89 through 103” have?

The most common answer is actinide (8 letters).

Crossword clue: any of a series of radioactive elements with atomic numbers 89 through 103

3 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

actinide 8 letters wn-def

any of a series of radioactive elements with atomic numbers 89 through 103

actinoid 8 letters wn-def

any of a series of radioactive elements with atomic numbers 89 through 103

actinon 7 letters wn-def

any of a series of radioactive elements with atomic numbers 89 through 103