Reactivity series (activity series) of metals

Typical order

A commonly used ordering, from most to least reactive, is given here as a practical reference. Slight variations appear in different sources depending on conditions and definitions.

1. Potassium (K)
2. Sodium (Na)
3. Calcium (Ca)
4. Magnesium (Mg)
5. Aluminium (Al)
6. Zinc (Zn)
7. Iron (Fe)
8. Tin (Sn)
9. Lead (Pb)
10. Hydrogen (H) — reference point
11. Copper (Cu)
12. Silver (Ag)
13. Gold (Au)
14. Platinum (Pt)

Why the series works

The ordering correlates with an element's tendency to be oxidised (to give up electrons). Physical and chemical factors such as ionization energy, standard electrode potential and the stability of the metal's oxide or salt influence position in the series. In practice, surface effects can modify apparent reactivity: for example aluminium is high in the series but forms a thin protective oxide that slows further reaction (passivation).

Uses and examples

• Predicting displacement: a metal higher in the series will displace the ion of a metal lower in the series from solution — e.g. iron will displace copper from copper(II) sulfate.
• Reactions with acids and water: metals above hydrogen typically react with dilute acids to produce hydrogen gas and with water to varying degrees; alkali metals react vigorously with water.
• Extraction and metallurgy: the series helps select reducing agents and processes for extracting metals from ores (metals lower in the series commonly occur native or require milder reduction).
• Corrosion and electrochemistry: it underpins understanding of sacrificial protection, galvanic cells and cathodic protection systems.

History, limits and cautions

The reactivity series emerged from experimental study of metal reactions and displacement experiments and is taught as a mnemonic and predictive aide. It is not an exhaustive theoretical hierarchy: actual reactivity depends on conditions (temperature, concentration, physical form) and on thermodynamic data such as electrode potentials. Reliable quantitative prediction uses electrochemical tables rather than a simple list. For deeper background consult general references on empirical series, metal chemistry and properties of metals, or resources describing chemical reactions involving metals.

Notable facts

Hydrogen is often included as a useful reference point: metals above hydrogen will typically liberate H2 from acids. Noble metals such as gold and platinum appear at the bottom because they resist oxidation and occur uncombined in nature, which is why they are valuable for jewellery and certain industrial catalysts.