Stoichiometric names

IR-5.2 Stoichiometric names of elements and binary compounds IR-5.3 Names of ions and radicals IR-5.3.1 General IR-5.3.2 Cations IR-5.3.2.1 General IR-5.3.2.2 Monoatomic cations IR-5.3.2.3 Homopolyatomic cations IR-5.3.2.4 Heteropolyatomic cations IR-5.3.3 Anions IR-5.3.3.1 Overview IR-5.3.3.2 Monoatomic anions IR-5.3.3.3 Homopolyatomic anions IR-5.3.3.4 Heteropolyatomic anions IR-5.4 Generalized stoichiometric names... 

The simplest type of compositional name is a stoichiometric name, which is just a reflection of the empirical formula (Section IR-4.2.1) or the molecular formula (Section IR-4.2.2) of the compound. In stoichiometric names, proportions of constituent elements may be indicated in several ways, using multiplicative prefixes, oxidation numbers or charge numbers. 

In some cases, a compound may be regarded as composed of constituents that may themselves be given names of any of several types (including stoichiometric names) the... 

A purely stoichiometric name carries no information about the structure of the species named. 

The stoichiometric name of the compound is then formed by combining the name of the electropositive constituent, cited first, with that of the electronegative constituent, both suitably qualified by any necessary multiplicative prefixes ( mono , di , tri , tetra , penta , etc., given in Table IV). The multiplicative prefixes precede the names they multiply, and are joined directly to them without spaces or hyphens. The final vowels of multiplicative prefixes should not be elided (although monoxide , rather than monooxide , is an allowed exception because of general usage). The two parts of the name are separated by a space in English. 

Stoichiometric names may correspond to the empirical formula or to a molecular formula different from the empirical formula (compare Examples 3 and 4 below). 

The charges of the atoms need not be specified in a stoichiometric name. In many cases, however, atoms or groups of atoms are known to carry a particular charge. Within compositional nomenclature, the name of a compound can include the names of individual ions constructed as stoichiometric names or according to other principles, as described below. 

Homopolyatomic cations are named by adding the charge number to the stoichiometric name of the corresponding neutral species, i.e. the element name with the appropriate multiplicative prefix. Radical dots may be added to indicate the presence of unpaired electrons. 

This principle for constructing generalized stoichiometric names parallels the principle for constructing generalized salt formulae in Section IR-4.4.3.4. However, the order of citation in a generalized stochiometric name is not necessarily the same as the order of symbols in the corresponding generalized salt formula, as is seen from Examples 4, 5 and 7 below. 

The following generalized stoichiometric names, based only on single-element constituents, do not carry information about the structure. 

When names of polyatomic ions occur as constituents in a generalized stoichiometric name, a certain amount of structural information is often implied by the name. 

The proportions of the constituents, be they monoatomic or polyatomic, may be indicated in generalized stoichiometric names by multiplicative prefixes, as was the case for the constituents of binary compounds (Section IR-5.2). ... 

Both compounds in Examples 1 and 2 have the overall formula T1I3 and both could be named by the simple stoichiometric name thallium triiodide. However, it is possible, and usually desirable, to convey more information in the name. 

Clearly, a simple stoichiometric name like potassium dioxide , although strictly speaking unambiguous (referring to the compound in Example 9), could easily be misinterpreted. In other cases, based on chemical knowledge, there is no chance of misinterpretation in practice, and the simple stoichiometric name will most often be used, as in Examples 11 and 12 below. 

Ba02 barium dioxide (simple stoichiometric name), or barium (dioxide)... 

IR-6.2.3.1 Stoichiometric names IR-6.2.3.2 Structural descriptor names IR-6.2.3.3 Systematic numbering of polyhedral clusters IR-6.2.3.4 Systematic naming giving hydrogen atom distribution IR-6.2.4 Heteronuclear parent hydrides... 

More structural information is obtained by augmenting the stoichiometric name by a structural descriptor. The descriptor is based on electron-counting relationships2 and is presented in Table IR-6.2. 

Substances are indexed under the lUPAC systematic stoichiometric name (i.e. with structural descriptors omitted) or the name generally used in the neutron scattering literature (even if obsolete or wrong) and cross referenced as needed. 

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