Synthetic Inorganic Chemistry

122 THE THEORY OF IONIZATION

charges the positive charges of the metal ions, we can eliminate

them from the equation, which then becomes simplified to:

Cu++ + Zn» -» Cu° 1 + Zn++

The metals, including hydrogen, may be arranged in the order in
which they tend to pass into the ionic condition, as, in this case,
zinc does at the expense of copper. Such a series is known as the
electromotive series, because the electromotive force of such
reactions, if properly disposed in a cell, may be made to send a
current through an external wire connector. (See Electromotive
Series, Appendix, page 353.)
A characteristic of metallic elements is that they can form simple
positive ions, but never simple negative ions. In other words, a
metal atom may lose one or more negative electrons, but it can
never attach to itself electrons in excess of those forming the make-
up of the unelectrified atom.
On the other hand, a characteristic of some of the most pro-
nouncedly non-metallic elements, fluorine, chlorine, bromine,
iodine, and sulphur, is that they can form simple negative ions.
No non-metal ever forms simple positive ions. The non-metals
may be arranged in a negative electromotive series.
The broadest, as well as the simplest, definition of oxidation is
the increasing of the positive valence of an element. This can be
accomplished only through the simultaneous and equivalent de-
crease of the valence of another element involved in the reaction.
The other element is said to be reduced. Thus oxidation and
reduction always occur together; one cannot occur alone. In the
above definition, positive valence is considered from an algebraic
standpoint. Thus iodine in an iodide is said to be oxidized when
its valence is changed from — 1 to 0; as, for example, in the re-
action
C1 2 °
21" ->2O +I 2 °

2K+ 2CF

If we take the viewpoint that valence is due to the attraction of
electrical charges on the atoms, the difference between reactions of
oxidation and reduction and of metathesis resolves itself into this:
oxidation and reduction involve a transfer of charges from one atom