1.1 What is Chemistry?

23.1. Electrochemical Cells http://www.ck12.org

The Activity Series

In the previous chapter, we looked at a number of oxidation-reduction reactions. We assumed that the reactions
occurred as written, but how do we know that a certain redox reaction will take place without actually running the
experiment? Which metals will react with water or acid? How do we know if one metal will undergo a single-
replacement reaction with a solution of a different metal cation?

Detailed study has made possible the construction of anactivity series, sometimes referred to as the electromotive
series, in which various neutral metals are ranked by their ability to lose electrons (to undergo oxidation). The most
reactive metals are listed at the top and will undergo a reaction simply by exposure to moisture. As we go down the
list, we find that some other metals will react with water, but only at elevated temperatures. Others will not react
with pure water but will undergo redox processes in the presence of acid. Finally, some of the least active metals are
inert even when submerged in very acidic solutions.

TABLE23.1:Activity Series

Metal Symbol Reactivity

Lithium

Potassium

Strontium

Calcium

Sodium

Li K

Sr

Ca

Na

Reacts with water, steam, and acids

to produce H 2 and metal hydroxides

Magnesium Aluminum

Zinc

Chromium

Mg

Al

Zn

Cr

Reacts with steam and acids to pro-

duce H 2 and metal hydroxides

Iron

Cadmium

Cobalt

Nickel

Tin

Lead

Hydrogen gas

Fe

Cd

Co

Ni

Sn

Pb

H 2

Will not react with water, but reacts

with acids to produce H 2 and metal

salts

Antimony

Arsenic

Bismuth

Copper

Sb

As

Bi

Cu

Will not react with water or acids to

form H 2 ; forms oxides with O 2

Mercury

Silver

Palladium

Platinum

Gold

Hg

Ag

Pd

Pt

Au

Found as a pure element in nature;

oxides decompose with heating

This table summarizes a lot of useful information. For example, cations of a given metal can be reduced back to their
elemental form by any more active metal (higher in the activity series), but not by less active metals. For example,
we can predict that the following reaction will occur spontaneously:

2 K + Mg^2 +→2 K++ Mg

Potassium is more active than magnesium. Potassium has a stronger driving force causing it to give up its valence