Explain why potassium is more reactive than sodium, giving the balanced chemical symbol equation for the reaction of potassium and water.

K + H₂O --> KOH + H_2Both potassium and sodium possess one electron in their outer shell. Both elements readily give up this unpaired electron and so for this reason are considered very reactive elements. Potassium is placed one period below sodium in period 4. Therefore, potassium has an additional shell of electrons and thus 8 more electrons. This extra shell of electrons shields the attractive force exerted on the outer electron by the nucleus. As a result, less energy is required to remove the outer electron of potassium and so it is more reactive.