Claim: A person who was known for his work in mass spectrometry discovered Uranium-235.
Evidence: It was discovered in 1935 by Arthur Jeffrey Dempster.
Arthur Jeffrey Dempster -LRB- August 14 , 1886 -- March 11 , 1950 -RRB- was a Canadian-American physicist best known for his work in mass spectrometry and his discovery of the uranium isotope 235U.