Order and meaning
A common order is K, Ca, Na, Mg, Al, Zn, Fe, Ni, Sn, Pb, (H), Cu, Hg, Ag, Pt, Au. Metals to the left give up electrons easily and become cations (oxidation); ions of metals to the right readily gain electrons and return to the metal (reduction).
Reactions it predicts
- Displacement: a more reactive metal placed in a solution of a less reactive metal's ions dissolves while the other metal is deposited, e.g. Zn + Cu²⁺ → Zn²⁺ + Cu.
- Water: K, Ca and Na react with cold water to release hydrogen, Mg with hot water, and Al, Zn and Fe with steam.
- Acids: metals above hydrogen release hydrogen from dilute hydrochloric or sulfuric acid; Cu and Ag do not.
Electrode potentials
The series is quantified by standard reduction potentials: the more negative E°, the more easily the metal is oxidised. Zn²⁺/Zn is about -0.76 V and Cu²⁺/Cu about +0.34 V. Aluminium often reacts more slowly than predicted because of its protective oxide layer.
Uses
Pairs of metals form cells such as the Daniell cell; zinc galvanising and sacrificial anodes protect iron and ships from corrosion; and the method used to extract a metal from its ore depends on its place in the series.
References
- Atkins, P., Overton, T., Rourke, J., Weller, M., & Armstrong, F. (2010). Shriver and Atkins' Inorganic Chemistry (5th ed.). Oxford University Press.
- Zumdahl, S. S., & Zumdahl, S. A. (2014). Chemistry (9th ed.). Cengage.
- Haynes, W. M. (Ed.). (2016). CRC Handbook of Chemistry and Physics (97th ed.). CRC Press.