Alexander Fleming.
Alexander Fleming (6 August, 1881 - 11 March, 1955) in 1928.
The penicillin was discovered by Alexander Fleming in the year 1928. He discovered it by chance when he was going to show some petri dishes to his former Lab Assistant D. Merlin Pryce.
Discovery of Penicillin is attributed to Alexander Fleming, a Scottish scientist.
For the history of discovering chemical elements see the link below.