single displacement occurs when an element takes the place of an element in a compound. Metals displace metals, nonmetals displace nonmetals. #1 no displacement; both reacants combined (synthesis) #2 the element, hydrogen, replaced the tungsten (displacment) #3 the cadmium and sulfur both combined with the oxygen (oxidation-reduction) #4 the element chromium displaced the hydrogen in the compound (displacement Solution single displacement occurs when an element takes the place of an element in a compound. Metals displace metals, nonmetals displace nonmetals. #1 no displacement; both reacants combined (synthesis) #2 the element, hydrogen, replaced the tungsten (displacment) #3 the cadmium and sulfur both combined with the oxygen (oxidation-reduction) #4 the element chromium displaced the hydrogen in the compound (displacement.