The numerical value of the charge on an ion (cation or anion), describing the
number of bonds which can be formed by the ion. Valencies may be respresented in
different ways, that is, descriptively (e.g. divalent), with numbers (e.g. 2-)
or with roman numerals (e.g. II) and may or may not include description of the
charge (- or +).
Examples of valancies are sodium (Na+) which is monovalent or univalent and
the carbonate ion (CO32-) which is divalent. Chrome can occur in -(II) to +(VI)
valencies, but is most common in the elemental (0), divalent (II), trivalent
(III) and hexavalent (VI) forms.
Source: GreenFacts
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The higher the valency, the greater the ability of a compound to combine with
other elements, such as hydrogen.
