Italicized element symbols

Single ligating atoms are indicated by the italicized element symbol preceded by a Greek kappa, K. These symbols are placed after the portion of the ligand name that represents the ring, chain or substituent group in which the ligating atom is found. 

Donor atoms of a particular element may be distinguished by adding a right superscript numerical locant to the italicized element symbol or, in simple cases (such as Example 3 below), a prime or primes. 

Metal-metal bonding is indicated by the italicized element symbols of the appropriate metal atoms, separated by an em dash and enclosed in parentheses, placed after the list of central atom names and before the ionic charge. The element symbols are placed in the same order as the central atoms appear in the name, i.e. with the element met last in the sequence of Table VI given first. The number of such metal-metal bonds is indicated by an arabic numeral placed before the first element symbol and separated from it by a space. For the purpose of nomenclature, no distinction is made between different metal-metal bond orders. 

Multiple bridging ligands between the pair of central atoms are cited in alphabetic order. Italicized element symbols indicating the coordinating atoms in bridging ligands are cited in the order of direction of the CRU and are separated by a colon ... 

Other methods for indicating or implying the presence of an atom in a nonstandard valence state have been used, especially the use of the prefix hydro e.g. 108). Such methods are sometimes convenient for simple molecules, but they are difficult to apply generally. A more general method that has seen extensive use utilizes the italicized symbol for the element with a superscript Roman numeral to indicate the valence (e.g. 109). This method has been objected to, however, because of ambiguity the superscript Roman number is also used to indicate oxidation number in inorganic compounds, and italicized atomic symbols are customarily used as locants for substituents. The A convention is a modification of the principle of this method, and avoids the objection. It was made a Provisional Recommendation of lUPAC in 1981. 

Note. In carbohydrate nomenclature, substitution at a heteroatom is normally indicated by citing the locant of the attached carbon atom, followed by a hyphen, and then the italicized heteroatom element symbol, e.g. 2-0-methyl, 5-N-acetyl. Substituents on the same kind of heteroatom are grouped (e.g. 2,3,4-tri-0-methy 1), and substituents of the same kind are cited in alphabetical order of heteroatoms (e.g. 5-N-acetyl-4,8,9-tri-0-acetyl). The alternative format with superscript numerical locants (e.g, N5,(/,(), ( -tetraacetyl), used in some other areas of natural product chemistry, is unusual in carbohydrate names. 

Some reaction names are preceded by element symbols they may be used as nouns or adjectives. When they are the first word of a sentence or appear in titles and headings, capitalize the first letter of the word. Do not italicize the element symbol. 

In Chemical Society practice, prefixes are italicized if, and only if, (i) they define the position of named substituents or (ii) they define a stereoisomer. Thus italics, by clause i) continue, for example, to be used for 0-, m-, p-, and for element symbols which denote substitution on that element, as in o-dichlorobenzene, A -methyl-2-napthylamine, etc. By clause (n), italics continue to be used for m-, trans-, JS-, /S-, etc. But italics are no longer used in names such as isobutane, isopropyl, t-butyl, for here, though the prefixes define the substance, they do not define named substituents. Similarly prefixes which have varied use are not italicized when in particular cases they refer to stereoisomers, as in allocinnamic acid, for here they do not define a particular stereoisomer. These rules differ somewhat from American practice. 

TABLE 11.20 Elements Precipitated by General Analytical Reagents This table includes the more common reagents used in gravimetric determinations. The lists of elements precipitated are not in all cases exhaustive. The usual solvent for a precipitating agent is indicated in parentheses after its name or formula. When the symbol of an element or radical is italicized, die element may be quantitatively determined by the use of the reagent in question. ... 

According to this notation, the main symbol in a formula shows the species (usually elements) present in a certain site. The -> vacancies are normally denoted by the italicized symbol V. Sometimes the vacant sites may also be indicated by other symbols, such as square box ( ), especially when the symbol ofvanadium (V) is present. The right lower indexes may indicate the species occupying this crystallographic site in an ideal lattice, or may show that this position is interstitial (subscript i). The second right lower index, if any, indicates the occupancy and should be separated by a comma. 

Rule 9. The italicized symbols for elements were recommended to indicate point of attachment. 

In a formula, the main symbols indicate the species present at a certain site, defined with respect to empty space. This will generally be the symbol of an element. If a site is vacant this is denoted by the italicized symbol V. (In certain contexts other symbols, such as a square box, , are used for vacancies, but the use of italicized V is preferred, the element vanadium being written with the upright letter V). 

By convention we refer to these molecules by their first letter (in italicized capitals to distinguish them from the symbols of chemical elements). A remarkable feature of these molecules is that all atoms lie on the same plane, the plane defined by the hexagonal ring, except for the two H atoms in the NH2 unit of C and the three H... 

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