Electrochemical Cell

In order to understand the intimate relationship between chemical reactions and electricity, we can consider a very simple oxidation-reduction reaction: the spontaneous reaction between a sodium atom and a chlorine atom to form sodium chloride:

What happens in this reaction is that an electron is passed from the sodium atom to the chlorine atom, leaving the sodium atom positively charged and the chlorine atom negatively charged. (Under normal conditions, the chlorine atoms are paired up into diatomic chlorine molecules, Cl₂; but that does not change the present argument.) When a large number of sodium atoms and chlorine atoms are mixed together and react, a large number of electrons move from sodium atoms to chlorine atoms. These moving electrons constitute a flow of electricity. The "push" or potential for this electron flow comes from the sodium atoms' eagerness to get rid of electrons and the chlorine atoms' relative eagerness to grab them.