Radioactive Element Discovered by Marguerite Perey

Puzzle 8 of Famous Women in Science Hard Pack

Question is: Radioactive Element Discovered by Marguerite Perey

and the answer is: FRANCIUM

Word Meaning:

FRANCIUM — The chemical element (symbol Fr) with an atomic number of 87. It is an intensely radioactive alkali metal that is not found in nature.

Definitions from Wiktionary.