Answer: 2
Explanation: Potassium, K, has only 1 valence electron, 4s^1. Oxygen, O, needs 2 more electrons to complete its valence shell to make 8 electrons. That means 2 K atoms will combine with 1 O atom, to produce K2O, potassium oxide. Both K electrons are stolen by the single O atom, so 2 electrons are transferred.