Page 87 - 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-5.4





                       Several conventions are observed for inferring oxidation numbers,  t he use of which is
                       particularly common in the names of compounds of transition elements. H  ydrogen is consi-
                       dered positive (oxidation number I) in combination with non-metallic elements and negative
                       (oxidation number  I) in combination with metallic elements. Organic g roups combined w ith
                       metal atoms are treated sometimes as anions (for example, a  m  ethyl ligand is usually
                       considered to be a  m  ethanide ion, CH 3 ), sometimes as neutral (e.g. carbon monooxide).

                       Bonds between  a toms of the same species make  n o  c ontribution to oxidation number.

                       Examples:

                          10. N 2 O                   n  itrogen(I) oxide
                                                      nitrogen(IV) oxide
                          11. NO 2
                                                      iron(II) diiron(III) oxide
                          12. Fe 3 O 4
                                                      manganese(IV) oxide
                          13. MnO 2
                          14. CO                      carbon(II) oxide
                                                      iron(II) sulfate
                          15. FeSO 4
                                                      iron(III) sulfate
                          16. Fe 2 (SO 4 ) 3
                                                      sulfur(VI) fluoride
                          17. SF 6
                                                      dioxidouranium(V) sulfate
                          18. (UO 2 ) 2 SO 4
                          19. UO 2 SO 4               dioxidouranium(VI) sulfate
                          20. K 4 [Fe(CN) 6 ]         p  otassium hexacyanidoferrate(II), or potassium
                                                      hexacyanidoferrate(4 )
                          21. K 4 [Ni(CN) 4 ]         p  otassium tetracyanidonickelate(0), o r  p otassium
                                                      tetracyanidonickelate(4 )
                          22. Na 2 [Fe(CO) 4 ]        s  odium tetracarbonylferrate( II), or sodium
                                                      tetracarbonylferrate(2 )
                          23. [Co(NH 3 ) 6 ]Cl(SO 4 )  h  exaamminecobalt(III) chloride sulfate,
                                                      or hexaamminecobalt(3þ) c hloride  s ulfate

                                                      iron(III) hexacyanidoferrate(II), or iron(3þ)
                          24. Fe 4 [Fe(CN) 6 ] 3
                                                      hexacyanidoferrate(4 )
                       Note that oxidation numbers are no longer recommended when  n aming homopolyatomic
                       ions. This is to avoid  a mbiguity.  O  xidation numbers refer to the individual atoms of the
                       element in question, e ven if they are appended to a  n ame  c ontaining a  m  ultiplicative prefix,
                       cf. E xample 12 above. To conform to this practice, dimercury(2þ) ( see Section IR-5.3.2.3)
                       would have to be named dimercury(I);  d  ioxide(2 )  ( see Section IR-5.3.3.3) would be
                       dioxide( I); and ions such as pentabismuth(4þ)  ( see Section IR-5.3.2.3) and dioxide(1 )
                       (see Section IR-5.3.3.3), with fractional f ormal oxidation numbers, could n ot be named at all.

           IR-5.4.2.3  Multiple  m  onoatomic  c onstituents vs. homopolyatomic constituents

                       Care should be taken  t o  d  istinguish between  m  ultiple  m  onoatomic  c  onstituents and
                       polyatomic constituents. This distinction is often not apparent from the formula, but is
                       tacitly implied.


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