Flexi Says: The activity series is a list of elements in decreasing order of their reactivity. Since metals replace other metals, while nonmetals replace other nonmetals, they each have a separate activity series. In case of metals, Potassium, Calcium, Sodium are some of the most reactive metals whereas copper, mercury and silver are some of the least reactive metals. Single-replacement reactions only occur when the element that is doing the replacing is more reactive than the element that is being replaced.
