Page 70 - Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005)
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IR-4.4                                                       F O R M  U L A E





                       For inorganic oxoacids, there is a  t raditional ordering  o f  f ormulae in which the ‘acid’ or
                       ‘replaceable’ hydrogen atoms (hydrogen atoms bound to oxygen) are listed fi rst, followed by
                       the central atom, then ‘non-replaceable’ hydrogen atoms (hydrogen atoms bound directly to
                       the central atom), and finally oxygen. This format is an alternative to writing the formulae as
                       coordination compound formulae (see Section IR-8.3).


                       Examples:
                          22. HNO 3 (traditional) or [NO 2 (OH)] (coordination)
                          23. H 2 PHO 3 (traditional) or [PHO(OH) 2 ] ( coordination)

                          24. H 2 PO 4 (traditional) or [PO 2 (OH) 2 ] (coordination)

                          25. H 5 P 3 O 10 (traditional) or [(HO) 2 P(O)OP(O)(OH)OP(O)(OH) 2 ] ( coordination)
                          26. (HBO 2 ) n (traditional) or (-B(OH)O)- n (coordination)

           IR-4.4.3.3  Chain compounds

                       For chain compounds containing three or more  d ifferent elements, the sequence of atomic
                       symbols should generally be in accord with the order in which the atoms are bound in the
                       molecule or ion, rather than using  a lphabetical order or order based on electronegativity.
                       However, if one wishes to view a  c  ompound formally as a  c  oordination  c  ompound,
                       e.g. in connection with a  d iscussion of additive naming of the compound, one may use
                       a  c oordination-compound  t ype of formula, as in Example 1  b elow.

                       Examples:





                           1. NCS or SCN (not CNS ) ¼ [C(N)S] , n itridosulfidocarbonate(1 )
                           2. BrSCN (not BrCNS)
                           3. HOCN (cyanic acid)
                           4. HNCO (isocyanic acid)
           IR-4.4.3.4  Generalized salt formulae

                       If the formula of a  c ompound containing three or more  e lements is not naturally assigned
                       using the preceding two sections, the compound can be treated as a  g eneralized salt. This
                       term is taken to mean any compound in which it is possible  t o  i dentify at least one
                       constituent  w  hich is a  p  ositive ion or can be classified as electropositive or more
                       electropositive than the other c onstituents, and at least one constituent w  hich is a  n egative
                       ion or can be classified as electronegative or more electronegative than the rest of the
                       constitutents. The ordering principle is then:

                       (i)  all electropositive constituents precede all electronegative constituents;
                       (ii)  within each of the two groups of constituents, alphabetical order is used.

                       Examples:

                           1. KMgF 3
                           2. MgCl(OH)


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