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IR-5.4                            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





                       Examples:
                                                      calcium bis(trioxidonitrate), or calcium nitrate
                           5. Ca(NO 3 ) 2
                                                      bis(dioxidouranium) tetraoxidosulfate
                           6. (UO 2 ) 2 SO 4
                                                      barium bis(tetrafluoridobromate)
                           7. Ba(BrF 4 ) 2
                           8. U(S 2 O 7 ) 2           uranium bis(disulfate)
                                                      tricalcium bis(phosphate)
                           9. Ca 3 (PO 4 ) 2
                                                      calcium diphosphate
                          10. Ca 2 P 2 O 7
                                                      calcium bis(hydrogencarbonate)
                          11. Ca(HCO 3 ) 2

           IR-5.4.2.2  Use of charge and oxidation numbers
                       It is possible t o  p rovide information on the proportions of the constituents in names by using
                       one of two other  d  evices: the charge number, which designates ionic charge, and the
                       oxidation number, which designates oxidation  s tate. In nomenclature, the use of the charge
                       number is preferred as the determination of the oxidation  n umber is sometimes ambiguous
                       and subjective. It is advisable to use oxidation numbers only when  t here is no uncertainty
                       about their assignment.
                         The charge number is a  n umber whose  m  agnitude is the ionic charge. It is written  i n
                       parentheses immediately after the name of an ion, without a  s pace. The  c harge is written  i n
                       arabic numerals, followed by the sign of the charge. Note that unity is always indicated,
                       unlike in superscript charge designations (which  a re used in formulae). No charge number is
                       used after the name  o f  a  neutral species.

                       Examples:

                           1. FeSO 4                  iron(2þ)  s ulfate
                                                      iron(3þ)  s ulfate
                           2. Fe 2 (SO 4 ) 3
                                                      dioxidouranium(1þ) s ulfate
                           3. (UO 2 ) 2 SO 4
                                                      dioxidouranium(2þ) s ulfate
                           4. UO 2 SO 4
                           5. K 4 [Fe(CN) 6 ]         p  otassium hexacyanidoferrate(4 )
                           6. [Co(NH 3 ) 6 ]Cl(SO 4 )  h  exaamminecobalt(3þ) c hloride sulfate

                       The oxidation number (see Sections IR-4.6.1 and IR-9.1.2.8) of an element is indicated by
                       a  R  oman numeral placed in parentheses immediately following the name (modified  b y
                       the ending ‘ate’ if necessary) of the element to which it refers. The oxidation number
                       may be positive, negative  o r  z ero (represented by the numeral 0). An oxidation number is
                       always non-negative unless the minus sign is explicitly used (the positive sign is never
                       used). Non-integral oxidation numbers are not used for nomenclature purposes.


                       Examples:
                           7. PCl 5                   phosphorus(V) chloride
                           8. Na[Mn(CO) 5 ]           s  odium pentacarbonylmanganate( I)
                           9. [Fe(CO) 5 ]             p  entacarbonyliron(0)


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