Nomenclature oxidation numbers

The Stock Oxidation-Number System. Stock sought to correct many nomenclature difficulties by introducing Roman numerals in parentheses to indicate the state(s) of oxidation, eg, titanium(II) chloride for TiCl2, iron(II) oxide for FeO, titanium(III) chloride for TiCl, iron(III) oxide for Fe203, titanium(IV) chloride for TiCl, and iron(II,III) oxide for Fe O. In this system, only the termination -ate is used for anions, followed by Roman numerals in parentheses. Examples are potassium manganate(IV) for K2Mn02, potassium tetrachloroplatinate(II) for K PtCl, and sodium hexacyanoferrate(III) for Na3Fe(CN)3. Thus a set of prefixes and terminations becomes uimecessary. 

The oxidation-number system is easily extended to include other coordination compounds. Even the interesting substances represented by the formulas Na4Ni(CN)4 and K4Pd(CN)4 create no nomenclature problem they become sodium tetracyanonickelate(0) and potassium tetracyanopaHadate(0), respectively. 

In chemical nomenclature, the oxidation number is sometimes called the Stock number for the German chemist Alfred Stock, who devised this numbering system. Oxidation numbers are discussed in more detail in Sections K and 2.9. 

What Do We Need to Know Already This chapter assumes that we know about atomic structure and electron configurations (Chapter 1), the basic features of energy, and the nature of the Coulomb interaction between charges (Section A). It is also helpful to be familiar with the nomenclature of compounds (Section D) and oxidation numbers (Section K). 

Stock system the nomenclature system using oxidation numbers to differentiate between compounds or ions of a given element. 

The Stock Oxidation-Number System. Stock sought to correct many nomenclature difficulties by introducing Roman numerals in parentheses to indicate the s(ate(s) of oxidation. 

Recognizing the empirical nature of oxidation numbers in inorganic chemistry nomenclature, and ending the use of this antiquated concept. 

There is no use of, no less dependence on, the admittedly empirical [87] concept of "oxidation number", as is the practice in IUPAC s inorganic nomenclature. 

The concept of oxidation number is interwoven into the fabric of inorganic chemistry in many ways, including nomenclature."... 

Moreover, the original concept of an integer number that quantified oxidation has remained the cornerstone of "inorganic chemistry" nomenclature — at least as it is practiced by IUPAC. [10] This is notwithstanding the fact that conceptual problems are attenuated when the familiar oxidation numbers that "work" for one compound (or ion) are used to determine the oxidation number of other compounds. 

At this point, several examples of how the concept of oxidation number has impacted chemical nomenclature are presented. 

C3O2 and C12O9. Each of these is incompatible with the simplistic idea upon which oxidation number is based namely, assigning oxidation numbers of +4/3 and +3/2 respectively to the carbon atom distorts an understanding of the actual chemistry. Instead, note that C3O2 is a linear molecule with structure 0 = C = C= C = 0, which is readily named in the proposed nomenclature as ... 

From these examples the rules of nomenclature are apparent. The central atom (like Fe, Cu, Co, Ag) is followed by the formula of the ligand (CN, NH3, H20, S203), with the stoichiometric index number, (which, in the case of monodentate ligands is equal to the coordination number). The formula is placed inside square brackets, and the charge of the ion is shown outside the brackets in the usual way. When expressing concentrations of complexes, brackets of the type will be used to avoid confusion. In the name of the ion, first the (Greek) number, then the name of the ligand is expressed, followed by the name of the central atom and its oxidation number (valency). 

In Chap. 6 we placed Roman numerals at the ends of names of metals to distinguish the charges on monatomic cations. It is really the oxidation number that is in parentheses. This nomenclature system is called the Stock system. For monatomic ions, the oxidation number is equal to the charge. For other cations, again the oxidation number is used in the name. For example, Hg2 + is named mercury(I) ion. Its charge is 24- the oxidation number of each atom is 4-1. Oxidation numbers are also used for other cations, such as dioxovanadium(V) ion, V02". The prefix 0x0- stands for oxygen. Oxidation numbers can be used with nonmetal-nonmetal compounds, as in sulfur(VI) oxide for SO3, but the older system using prefixes (Table 6-2) is still used more often. 

The oxidation number (see Sections IR-4.6.1 and IR-9.1.2.8) of an element is indicated by a Roman numeral placed in parentheses immediately following the name (modified by the ending ate if necessary) of the element to which it refers. The oxidation number may be positive, negative or zero (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. 

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