The reactivity of metals can be found out by using voltage data obtained from galvanic cells. According to the available data the reactivity of metals depends upon how readily it is oxidized or lose electrons to form positive ions. If a galvanic cell is established between two metals, the more reactive metal will lose electrons and form positive ions. The voltage generated by this cell measures the comparative tendencies of the metals to lose electrons. A higher voltage indicates that the difference in the tendency of one metal (more reactive metal) to lose electron is far more than the other.
If a cell is established between magnesium and copper it produces a higher voltage than a cell established between iron and copper. This will mean that magnesium is more reactive than iron because it has a tendency to lose electrons more easily.
By measuring the voltage produced when different metal pairs are used in a voltaic cell, it is possible to determine the reactivity series of metals which is called electrochemical series. Metals placed higher in this series are considered more reactive and easily lose electrons than the metals placed lower in the series.
🔋 Electrochemical series: higher metals spontaneously reduce ions of lower metals.