a natural push for copper to lose electrons more than for the silver to lose
electrons. Elements higher on the activity series then are simply those that have a
stronger desire to lose electrons than the ones below them.
Sample Problem
Using the activity series for metals found in Chapter 8, predict which of the
following reactions is likely to occur as written. Also, for any reaction that does
occur, describe the substances involved in the oxidation process as well as those
involved in the reduction process.
Au(s) + CuCl 2 (aq) → Cu(s) + AuCl 2 (aq)
3Zn(s) + 2FeCl 3 (aq) → 3ZnCl 2 (aq) + 2Fe(s)The first reaction will not occur (spontaneously). The activity of gold is
lower than that of copper, so gold will not replace copper in a compound. In other
words, gold has a lesser desire to lose electrons than does copper. The second
reaction will occur. Zinc is more active than iron. In this reaction the zinc will be
oxidized, or lose electrons, as the reaction occurs. The recipient of electrons lost
by the zinc is the iron. Therefore, the iron will be reduced.
OXIDATION STATES
Because the transfer of electrons in chemical reactions is so prevalent, chemists
have developed a manner to keep track of their movement. It’s important to note
that for processes involving ionic species, of the type we have looked at so far, it
is somewhat straightforward to distinguish redox from non-redox: The sign and
magnitude of the charge on the ions involved allows for an easy view of what is
taking place. Using the spontaneous reaction between zinc and iron(III) chloride
referenced in the previous section, the zinc started as an atom with no net charge
and turned into an ion with a 2+ charge. During chemical reactions, in order for
the charge on particles to increase, negative electrons have to be lost and the
process of oxidation occurs. A similar analysis of the iron in the reaction shows
that the iron began as a 3+ ion (ferric) and ended as a neutral iron atom in the
products. In other words, the iron went down in charge. Particles that go down in
charge do so by gaining negative electrons. This description gives insight to why
the process is referred to as reduction despite the fact that electrons are being
gained. Reduction refers to the change in charge involving ionic species, not to
the change in the number of electrons possessed by a particle as a result of the
process taking place. Since reduction involves a decrease in charge, oxidation
must involve an increase in charge (when ionic species are involved). Using the
term oxidation may seem like a strange way to describe this process, but its use
will be better understood from a historical context when combustion reactions