Number Roman numerals

For compounds or ions containing elements that have a variable oxidation number, Roman numerals are used to indicate the oxidation number of the element concerned, and so name the chemical species. This is called Stock notation, after the chemist A. Stock who devised the method. 

Names of monoaromic cations. Monoaromic cations are named by adding in parentheses after the rume of the element [either the appropriate charge number followed by the plus sign or the oxidation number (Roman numeral)] followed by the words cation or ion ... 

At least two dozen different risk assessment code (RAC) matrices are in use. They all are based on severity on one axis and probability on the other, but the size and layout of individual matrices vary significantly. Some have severity on the vertical axis others have it on the horizontal axis. One makes the low numbers bad (an RAC of 1 indicates a high probability of a catastrophic accident), whereas the next uses a 1 to indicate a very remote probability of an insignificant loss. Some use RACs from 1 to 4 others use 1 to 16 still others use a combination of numbers, roman numerals, and/or letters (II to 4V or lA to 5D). 

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. 

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. 

The vertical columns are known as groups. Historically, many different systems have been used to designate the different groups. Both Arabic and Roman numerals have been used in combination with the letters A and B. The system used in this text is the one recommended by the International Union of Pure and Applied Chemistry (IUPAC) in 1985. The groups are numbered from 1 to 18, starting at the left. 

As you can deduce from the preceding examples, the oxidation number of the central metal ion is indicated by a Roman numeral written at the end of the name. 

The apothecaries system uses whole numbers and fractions. Decimals are not used in this system. The whole numbers are written as lowercase Roman numerals, for example, x instead of 10, or v instead of 5. 

When setting up tiie proportion, the apothecaries system was written in Arabic numbers instead of Roman numerals, and their order was reversed (1 gr instead of gr i) so that all numbers and abbreviations are uniform in presentation. 

The name of a monatomic cation is the same as the name of the element forming it, with the addition of the word ion, as in sodium ion for Na+. When an element can form more than one kind of cation, such as Cu+ and Cu2+ from copper, we use the oxidation number, the charge of the cation, written as a Roman numeral in parentheses following the name of the element. Thus, Cu+ is a copper(I) ion and Cu2+ is a copper(II) ion. Similarly, Fe2+ is an iron(II) ion and Fe3" is an iron(III) ion. As shown in Fig. C.6, most transition metals form more than one kind of ion so unless we are given other information we need to include the oxidation number in the names of their compounds. 

The name of a monatomic cation is the name of the element plus the word ion for elements that can form more than one type of cation, the oxidation number, a Roman numeral indicating the charge, is included. 

Step 1 Identify the cation and the anion (see Table D.l or Appendix 3A, if necessary). To determine the oxidation number of the cation, decide what cation charge is required to cancel the total negative charge of the anions. Step 2 Name the cation. If the metal can have more than one oxidation number (most transition metals and some metals in Groups 12 through 15/V), give its charge as a Roman numeral. 

A Roman numeral denotes the oxidation number of the central metal ion ... 

If the complex has an overall negative charge (an anionic complex), the suffix -ate is added to the stem of the metal s name. If the symbol of the metal originates from a Latin name (as listed in Appendix 2D), then the Latin stem is used. For example, the symbol for iron is Fe, from the Latin ferrum. Therefore, any anionic complex of iron ends with -ferrate followed by the oxidation number of the metal in Roman numerals ... 

Figure 1. An unrooted phylogenetic tree of the myosins based on the amino acid sequence comparison of their head domains demonstrating the division of the myosin superfamily into nine classes. The lengths of the branches are proportional to the percent of amino acid sequence divergence and a calibration bar for 5% sequence divergence is shovk n. The different classes of myosins have been numbered using Roman numerals in rough order of their discovery and hypothetical models of the different myosin structures are shown. Question marks indicate either hypothetical or unknown structural features, and only a fraction of the known myosins are shown. (Taken, in modified form, from Cheney et al., 1993).

Further subdivision of a five-digit slice utilizes lower-case Roman numerals in parentheses (i), (ii), (iii), etc. It is often found that as a consequence of the organization, cognate material is located in different chapters but in similarly numbered pieces, i.e., in parallel sections. Section numbers, rather than page numbers, are the key by which the material is accessed through the various indexes. 

Note that the Roman numeral subscripts refer to numbered reactions and have nothing to do with iodine. All these examples have involved elementary reactions. Multiple reactions and apparently single but nonelementary reactions are called complex. Complex reactions, even when apparently single, consist of a number of elementary steps. These steps, some of which may be quite fast, constitute the mechanism of the observed, complex reaction. As an example, suppose that... 

After the name of the metal, give the oxidation number of the metal in parentheses as a Roman numeral or as 0 if the oxidation number is zero. 

In pharmaceutical and medical device development, clinical trials are classified into four main phases designated with Roman numerals 1,11, III and lY The various phases of development trials differ in purpose, length and number of subjects involved. Phase I trials are conducted to determine safe dose levels of a medication, treatment or product (National Institutes of Health, 2002). The main purpose is often to determine an acceptable single dosage - how much can be given without causing serious side-effects. Phase I trials will also involve studies of metabolism and bioavailabity (Pocock, 1983). The sample size of a Phase 1 clinical trial is usually small, ranging from 10-80 subjects (National Institutes of Health, 2002 Pocock, 1983). 

The Roman numerals in the parentheses indicate coordination numbers for which the ionic radii are given here. 

Table 6.4 Ionic radii for transition elements according to SHANNON [69], based on r(02 ) = 140 pm. Numbers with signs oxidation states Is = low spin, hs = high spin roman numerals coordination numbers if other than 6...

Naming of the positive ion depends on whether the cation is monatomic (has one atom). If not, the special names given in Sec. 6.3.2 are used. If the cation is monatomic, the name depends on whether the element forms more than one positive ion in its compounds. For example, sodium forms only one positive ion in all its compounds—NaT Iron forms two positive ions—Fc2r and Fe,+. Cations of elements that form only one type of ion in all their compounds need not be further identified in the name. Thus, Na may simply be called the sodium ion. Cations of metals that occur with two or more different charges must be further identified. Fe(NO,)2 and Fe(NO,)3 occur with Fc2+ and Fe3 ions, respectively. If we just call the ion the iron ion, we will not know which one it is. Therefore, for monatomic cations, we use a Roman numeral in parentheses attached to the name to tell the charge on such ion. (Actually, oxidation numbers are used for this purpose, but if you have... 

The central sulphur has eight bonds. The ion has an overall charge of —2. The oxidation number of the sulphur is therefore 8 — 2 = +6. We generally indicate oxidation numbers with roman numerals, though, so we write S(VI). Table 2.10 lists the rules required to assign an oxidation number. 

Care we write a formal charge with Arabic numerals, and means that the full charge exists as indicated Cu2+ means a copper atom with fully two electronic charges missing. We write an oxidation number with Roman numerals, and does not relate to any physical loss or gain of electrons it is purely a book-keeping exercise. Mnvn does not mean that a manganese atom has lost seven electrons. 

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