Page 79 - Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005)

C O M P O S I T I O N A L N O M E N C L A T U R E I R-5.3

silicon tetrachloride
9. SiCl 4
tricalcium diphosphide, or calcium phosphide
10. Ca 3 P 2
11. NiSn nickel stannide
12. Cu 5 Zn 8 pentacopper octazincide
tricosachromium hexacarbide
13. Cr 23 C 6
Multiplicative prefixes n eed not be used in binary names if there is no ambiguity a bout the
stoichiometry of the compound (such a s i n E xample 10 above). T he prefix ‘mono’ is, strictly
speaking, superfluous and is only needed f or emphasizing stoichiometry when discussing
compositionally related substances, such as Examples 2, 3 a nd 4 a bove.
Alternatively, proportions of constituents may be indicated by using o xidation numbers
or charge numbers (Section IR-5.4.2).
For compounds containing more t han two elements, f urther conventions are required t o
form a c ompositional name (see Sections IR-5.4 and IR-5.5).

IR-5.3 N A M E S O F I O N S A N D R A D I C A L S

IR-5.3.1 General

The charges of the atoms need not be specified in a s toichiometric name. In many c ases,
however, a toms or groups of atoms are known to carry a particular charge. Within
compositional nomenclature, the name of a c ompound can include the names of individual
ions constructed as stoichiometric names or according to other p rinciples, as described
below.

IR-5.3.2 Cations

IR-5.3.2.1 General

A c ation is a m onoatomic or polyatomic species having one or more positive charges. The
charge on a c ation can be indicated in names by using the charge number or, in the case of
additively named cations, b y t he oxidation number(s) of the central atom or atoms.
Oxidation a nd charge numbers are discussed i n S ection IR-5.4.2.2.

IR-5.3.2.2 Monoatomic cations
The name of a m onoatomic cation is that of the element with an appropriate charge number
appended in parentheses. Unpaired electrons in monoatomic cations may be indicated using
a r adical dot, i.e. a c entred dot placed in front of the charge, preceded by a n umber
if necessary.

Examples:
1. Na þ sodium(lþ)
2. Cr 3þ chromium(3þ)

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