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