Ionic charge nomenclature

Elemental composition, ionic charge, and oxidation state are the dominant considerations in inorganic nomenclature. Coimectivity, ie, which atoms are linked by bonds to which other atoms, has not generally been considered to be important, and indeed, in some types of compounds, such as cluster compounds, it caimot be appHed unambiguously. However, when it is necessary to indicate coimectivity, itaUcized symbols for the connected atoms are used, as in trioxodinitrate(A/,A/), O2N—NO . The nomenclature that has been presented appHes to isolated molecules (or ions). Eor substances in the soHd state, which may have more than one crystal stmcture, with individual connectivities, two devices are used. The name of a mineral that exemplifies a particular crystal stmcture, eg, mtile or perovskite, may be appended. Alternatively, the crystal stmcture symmetry, eg, rhombic or triclinic, may be cited, or the stmcture may be stated in a phrase, eg, face-centered cubic. 

In compositional nomenclature, ligands are given in alphabetical order before central atoms. Central atoms are listed in alphabetical order as well. Bridging ligands to the extent known are indicated by the p notation (see Section 3.2.3.4). The numbers of ligands and central atoms are indicated by the appropriate numerical prefixes (see Section 3.3.2). Anions, cations, oxidation states and ionic charges are indicated in the same manner as in mononuclear compounds (see Section 3.3.3). For examples see Table 14. 

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. 

In the Stock system (systematic name), a Roman numeral indicates the magnitude of the cation s charge. In the older common nomenclature system, the suffix -ous indicates the lower ionic charge, and the suffix -ic indicates the higher ionic charge. Consider the examples in Table 4.1. 

Some metal atoms, especially those of transition and inner-transition elements, form more than one type of charged ion. Copper, for example, forms both Cu and Cu, and iron forms Fe and Fe. The names of ionic compounds containing such elements must indicate which ion is present in the compound. A nomenclature system that does this well indicates the ionic charge of the metal ion by a roman numeral in parentheses following the name of the metal. Thus, CuCl is copper(l) chloride and CUCI2 is copper(ll) chloride. These names are expressed verbally as copper one chloride and copper two chloride. ... 

In a more comprehensive treatment of nomenclature, compounds containing ions that exhibit more than one charge have the ionic charge indicated by the Roman numeral. For example, Sn and Pb are not transition metals, but their names require a Roman numeral because their charge can vary from one compound to another. 

In Section 1, we introduced the use of Roman numerals to denote ionic charges in the Stock system of naming ionic compounds. The Stock system is actually based on oxidation numbers, and it can be used as an alternative to the prefix system for naming binary molecular compounds. In the prefix system, for example, SO2 and SO3 are named sulfur dioxide and sulfur trioxide, respectively. Their names according to the Stock system are sulfur(IV) oxide and sulfur(VI) oxide. The international body that governs nomenclature has endorsed the Stock system, which is more practical for complicated compounds. Prefix-based names and Stock-system names are still used interchangeably for many simple compounds, however. 

For the thermodynamics this nomenclature problem must of course be without consequence. If, in the situation of fig. 3.1b or d, the charge attributed by the adsorbed ionics is interpreted as a specifically adsorbed charge a , the Gibbs energy of the layer may be written as... 

The nomenclature is confusing and its use confused, as an examination of the literature reveals. By exoergic charge-transfer reaction, we imply that the formal chemical reaction A B,A)B is exoergic for ground-state products. If the transfer of the electron is resonant or accidentally resonant, the ionic product will normally be formed in an excited electronic and/or vibrational state such that the actual electron transfer will be thermoneutral or essentially so. The exoergicity is released subsequently by the decay of the excited B product ion. 

For certain purposes (e.g. nomenclature), chemists like to work out the charges that the atoms in a compound would have if all the bonds were completely polarized and the bonding was ionic. This can be done as follows ... 

The cations formed as shown by the half-reactions above are simply given the names of the metals that produced them, such as sodium for Na+ and calcium for Ca +. Since they consist of only one element, the name for each anion has an -ide ending, that is, hP", nitride CP , oxide S , sulfide H , hydride F, fluoride and Cl , chloride. An advantage in the nomenclature of ionic compounds is that it is not usually necessary to use prefixes to specify the numbers of each kind of ion in a formula unit. This is because the charges on the ions determine the relative numbers of each, as shown by the examples in Table 4.3. 

Except for those compounds in which the cation is H+ (adds) or the anion is OH (bases), the compounds that consist of a cation and an anion are salts. Therefore, the rules of nomenclature discussed for ionic compounds in Section 4.8 are those of salts. The salt product of Reaction 4.9.6, above, consists of K+ cation and Cl anion, so the salt is called potassium chloride. The salt product of Reaction 4.9.7, above, is made up of Ca + cation and S04 anion and is called calcium sulfate. The reaction product of LiOH base with H2SO4 add is composed of Li+ ions and SO42 ion. It takes 2 singly charged Li+ ions to compensate for the 2- charge of the S04 anion, so the formula of the salt is Li2S04. It is called simply lithium sulfate. It is not necessary to call it dilithium sulfate, because the charges on the ions denote the relative numbers of ions in the formula. 

The nomenclature, or naming system, of binary ionic compounds involves combining the names of the compound s positive and negative ions. The name of the cation is given first, followed by the name of the anion. For most simple ionic compounds, the ratio of the ions is not indicated in the compound s name, because it is understood based on the relative charges of the compound s ions. 

In Chapters 2 and 3, we considered the history, nomenclature, and structures of coordination compounds. In these earlier discussions, we introduced the metal-ligand (M-L) coordinate-covalent bond in which the ligand shares a pair of electrons with the metal atom or ion. Now we are in a position to consider the nature of the M-L bond in greater detail. Is it primarily an ionic interaction between ligand electrons and a positively charged metal cation Or should the M-L bond be more properly described as predominantly covalent in character Whatever the character of the bond, the description of M-L interactions must account for (1) the stability of transition metal complexes, (2) their electronic and magnetic characteristics, and (3) the variety of striking colors displayed by these compounds. 

In this symbol, three pieces of information are depicted. The center designates the species of interest (zinc). The subscript tells us what crystal site that species sits in (interstitial), while the superscript tells us the effective charge ( + l). The effective charge is relative to that of the site in the perfect lattice. For example, consider a crystal of NaCl. The sodium normally gives up a valence electron to chloride to form the ionic bonds in the lattice. However, if a calcium atom exists as a substitutional impurity in a sodium site, it may lose both its valence electrons. Its effective charge, relative to the sodium that would normally sit there, is then +1. The nomenclature for such an impurity would be written as Cajjja. ... 

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