Page 68 - Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005)
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IR-4.4                                                       F O R M  U L A E





                       Examples:

                           1. NH 3
                           2. H 2 S

                           3. OF 2
                           4. O 2 Cl

                           5. OCl
                                 þ
                           6. PH 4
                                  4
                           7. P 2 O 7
                           8. [SiAs 4 ] 8
                           9. RbBr
                          10. [Re 2 Cl 9 ]

                          11. HO or OH
                          12. Rb 15 Hg 16
                          13. Cu 5 Zn 8 and Cu 5 Cd 8

                       Note that the formula  f or the hydroxide ion should  b e  H  O to be consistent with the above

                       convention.
                         Ordering by electronegativity could, in principle, be applied to ternary, quaternary, etc.
                       species. F or most species consisting of more  t han two elements, however, o ther criteria for
                       ordering  t he element symbols in the formula are more often used (see Sections IR-4.4.3.2 to
                       IR-4.4.3.4).

           IR-4.4.3.2  Formal treatment as coordination compounds
                       The nomenclature of coordination compounds is described in detail in Chapter I R-9. A  b rief
                       summary of the construction of formulae of coordination compounds is given  h ere. M  any
                       polyatomic  c ompounds may conveniently be treated as coordination compounds for the
                       purpose  o f c onstructing a  f ormula.
                         In the formula of a  c oordination  e ntity, t he symbol of the central atom(s) is/are placed
                       first, followed by the symbols or formulae of the ligands, unless additional structural
                       information can be presented by changing the order (see, for example, Section IR-4.4.3.3).
                         The order of citation of central atoms is based on electronegativity as described in
                       Section IR-4.4.2.1. Ligands are cited alphabetically (Section IR-4.4.2.2)  a ccording to the
                       first symbol of the ligand formula or ligand abbreviation (see Section IR-4.4.4) as written.
                       Where possible, the ligand formula  s hould  b e  w  ritten in such a  w  ay that a/the donor atom
                       symbol is closest to the symbol of the central atom to which it is attached.
                         Square brackets  m  ay be used to enclose the whole  c oordination entity  w  hether c harged
                       or not. Established practice is always to use square  b rackets for coordination entities  w  ith
                       a  t ransition metal as the central atom (cf. S ections IR-2.2.2 and IR-9.2.3.2).

                       Examples:

                           1. PBrCl 2
                           2. SbCl 2 F  o r  [ SbCl 2 F]


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