USA's Aly Raisman took gold in the Olympic women's floor to prevent Romania winning the exercise for a third successive Games.
Raisman, 18, scored 15.600 to claim her second London 2012 gold after
helping USA win the team event.
Romania's Athens 2004 gold medallist Catalina Ponor finished second with 15.200, but defending champion Sandra Raluca Izbasa came eighth.
Russian teenager Aliya Mustafina won bronze at the North Greenwich Arena.
Mustafina, 17, scored 14.900 to take third place ahead of Italy's Vanessa Ferrari, whose routine was also worth 14.900 but given a lower execution rating.
Kseniia Afanaseva was bidding to become the first woman since 1988 to win Olympic gold as reigning world champion, but the Russian could only finish sixth with her score of 14.566 in the opening routine.
Earlier on Tuesday, Raisman beat Ponor to
bronze in the beam.