When a potassium atom reacts with bromine, the potassium atom will

a. lose only 1 electron

b. lose 2 electrons

c. gain only 1 electron

d. gain 2 electrons?

The potassium will lose an electron and the bromine will gain one. This works because it gives them both a noble gas base, which is extremely stable.

For future reference, these are the most common stable configurations: Noble Gas Core (far right on periodic table), half filled shells, empty shells, and eright electrons in a D electron cloud (transition metals, aka b section or numbers 3 - 12 on modern tables)