Simplify the following text for a Grade 8 native English-speaking person.
Original: Marie SkÅ odowska Curie ( 7 November 1867 â `` 4 July 1934 ) was a Polish-born French physicist and chemist famous for her work on radioactivity .
Simplified: Marie SkÅ odowskaâ `` Curie ( 7 November 1867 â `` 4 July 1934 ) was a physicist and chemist .