Page 66 - Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005)

IR-4.3 F O R M U L A E

Where several polymorphs crystallise in the same crystal system they may be differentiated
by the Pearson s ymbol (see Sections IR-3.4.4 and IR-11.5.2). Greek letters are frequently
employed t o d esignate polymorphs, but their use is often confused and contradictory and is
not generally recommended.

Examples:

1. TiO 2 (t) ( anatase type)
2. TiO 2 (t) ( rutile type)
3. AuCd(c), or AuCd (CsCl type)

For the formulae of solid solutions and non-stoichiometric phases, see Chapter IR-11.

IR-4.3 I N D I C A T I O N O F I O N I C C H A R G E

Ionic charge is indicated by means of a r ight upper index, as in A nþ or A n (not A þn or
n
A ). If the formula i s p laced in enclosing marks, the right upper index i s p laced outside the
enclosing marks. For p olymeric ions, t he charge of a s ingle repeating unit should be placed
inside the parentheses that comprise the polymeric structure or the total charge of the
polymeric species should be placed outside the polymer parentheses. (The rules needed f or
ordering t he symbols in some of the example f ormulae below are given in Section IR-4.4.3.)

Examples:
1. Cu þ

2. Cu 2þ
3. NO þ
4. [Al(OH 2 ) 6 ] 3þ
þ
5. H 2 NO 3
6. [PCl 4 ] þ
7. As 3

8. HF 2
9. CN
2
10. S 2 O 7
11. [Fe(CN) 6 ] 4
12. [PW 12 O 40 ] 3
5
5
13. [P 3 O 10 ] , o r [ O 3 POP(O) 2 OPO 3 ] , o r
5 _
O O O
O P P O O P O

O O O

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