Activity series of metals

Metals	Metal Ion	Reactivity
K	K⁺	reacts with water
Ca	Ca²⁺
Na	Na⁺
Mg	Mg²⁺	reacts with acids
Al	Al³⁺
Zn	Zn²⁺
Fe	Fe²⁺
Ni	Ni²⁺
Sn	Sn²⁺
Pb	Pb²⁺
H₂	H⁺
Cu	Cu²⁺	highly unreactive
Hg	Hg²⁺
Ag	Ag⁺
Au	Au³⁺

Metals are listed in decreasing ease of oxidation, or increasing ease of reduction. A metal can replace metals listed below it in the activity series, but not above. For example, sodium is highly active and thus able to replace hydrogen from water:

2 Na (s) + 2 H₂O (l) -> 2 NaOH (aq) + H₂ (g)

Metals that can replace hydrogen within acids but not water are listed in the middle of the activity series, for example zinc replaces hydrogen in sulfuric acid:

Zn (s) + H₂SO₄ (aq) -> ZnSO₄ (aq) + H₂ (g)

The activity series has applications in electrochemistry, where two dissimilar metals are chosen as electrodes of a battery.

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Activity series of metals