Roman numerals, metal ions

Transition metal that requires a Roman numeral. Fe " ion balances three N03 ions. 

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 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. 

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

Oxidation state is a frequently used (and indeed misused) concept which apportions charges and electrons within complex molecules and ions. We stress that oxidation state is a formal concept, rather than an accurate statement of the charge distributions within compounds. The oxidation state of a metal is defined as the formal charge which would be placed upon that metal in a purely ionic description. For example, the metals in the gas phase ions Mn + and Cu are assigned oxidation states of +3 and +1 respectively. These are usually denoted by placing the formal oxidation state in Roman numerals in parentheses after the element name the ions Mn- " and Cu+ are examples of manganese(iii) and copper(i). 

MgCls Magnesium is a metal that always forms a +2 ion. This ionic compound is named without Roman numerals or prefixes magnesium chloride. 

Some metals, such as iron, can form more than one type of ion. Iron ions can either have a +2 or a +3 charge. Chemists use Roman numerals to distinguish between the two different types of iron ions. The Roman numeral II in the name of the chemical compound iron(II) sulfide means that the iron ion in this compound has a +2 charge. 

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... 

Am. In each ease, the answer is BuS. Part (ft) gives the ions and their charges, and so is perhaps easiest to answer. Part (know that periodic group IIA elements always form 2-t- ions in all their compounds and that sulfur forms a 2- ion in its compounds with metals. It is also necessary to remember that the metal is named first. In part (< ). the fact that there is only one compound of these two elements is deduced by the fact that the barium is stated with no Roman numeral, and that sulfide is a specific ion with a specific (2-) charge. 

Use Roman numerals to designate the oxidation state of the metal ion [cobalt(III)]. 

To avoid the necessity of memorizing a separate name for each ion, we can use the Stock system. In the Stock system, the charge of the cation appears as a Roman numeral immediately after the name of the element. Using the Stock system, we write Fe2+ as the iron(II) ion, and Cu+ as the copper(I) ion. Other than the necessity of indicating the charges, there are no differences between the naming of transition metal compounds and other compounds of the metals. So while KC1 is potassium chloride, CuCl is copper(I) chloride. 

If the metal ion may exist in more than one oxidation state, this oxidation state should be listed, in Roman numerals, immediately after the name of the metal ion. The Roman numeral is enclosed in parentheses and is considered part of the same word, and not a separate grouping. If the metal occurs in only one oxidation state, no such indicator is used. This notation is the Stock system discussed earlier. 

Note According to the Stock system, metallic ions are named using Roman numerals. The Roman numeral shows the charge on the metal ion titanium(IV) W copper(l), Cu manganese(VIl), Mn +... 

Many researchers refer to stems 1, 2, and 3 using their Roman numeral equivalents—that is, stems I, II, and III. These motifs are also denoted as helices I, II, and III. It should be noted at the beginning of this hammerhead ribozyme discussion that structure-function relationships, the role of various nucleobases, metal ion participation in catalysis, and other features of the system have not been completely delineated and in some cases remain controversial. Globally, the hammerhead fold appears to be similar in both solution and solid-state studies. In solution, however, the central core of the hammerhead construct appears to be highly dynamic. This may account for different experimental results among the analytical techniques used in solution and certainly explains some distinct differences seen between solution and solid-state (X-ray crystallographic) structures. 

Lithium nitrate. Because lithium is an alkali metal and the charge of alkali metals in Group I is always -i-l, you don t need to use Roman numerals to indicate the charge of lithium. You simply write lithium and then the name of the polyatomic ion, which is nitrate. You don t change the ending of the polyatomic ion ncime. 

Pb(S04)2 The cation lead is a metal with a variable charge, as indicated by the Roman numeral IV in parentheses. This classification means that lead has a charge of +A. SO is the polyatomic ion sulfate with a charge of -2. To balance out the charges, you need two sulfate ions for each lead ion. Thus, the formula has one Pb ion with a total charge of -1-4 and two sulfate ions with a total charge of -A. To indicate the need for two polyatomic ions, you put pcirentheses around the sulfate ion and write the 2 as a subscript outside the parentheses. 

The thing about transition metals is that the same transition metal can form cations with different charges. Differently charged metal cations need different names so chemists don t get any more confused than they already are. These days, you indicate these differences by using Roman numerals within parentheses to denote the positive charge of the metal ion. However, an older method adds the suffix -ous or -ic to indicate the cation with the smaller or larger charge, respectively. For example ... 

Lithium (group 1A) forms only the Li+ ion and does not need a Roman numeral. Potassium (group 1A) forms only the K+ ion. The carbonate ion has a —2 charge, so copper must be +2. A Roman numeral is needed because copper, a transition metal, can form more than one ion. 

A complex ion or nonionic molecule carries the name of the central metal last, with its oxidation state (charge per atom) in Roman numerals (or 0) enclosed in parentheses. (A detailed discussion of oxidation state is provided in Chapter 11.)... 

Many metals may form cations of more than one charge. In this case, a Roman numeral in parenthesis after the name of the element is used to indicate the ion s charge in a particular compound. 

Transition elements form ions with more than one charge, i.e. they have ions of different charges nd that is indicated as a Roman numeral in paranthesis next to the metal, e.g Fe (I) etc. 

Naming of Coordination Sphere In naming the complex, the names of the ligands are written first followed by the name of the central ion. The oxidation number of the central metal atom is expressed by Roman numeral in parentheses just after the name of the central metal atom. The sequence of naming coordination sphere is summed up as ... 

Q The name of the complex ion, whether it is an anion, cation, or neutral, is written as two parts that are combined into one word. The first part consists of the name of the ligand, and the second part, the name of the metal ion. If more than one of the same type of ligand appears, Greek prefixes are used to indicate the number of times the ligand occurs. A Roman numeral is used to indicate the charge on the cation. For instance, the name of the ion in the previous example, Fe(CN)64, is hexacyanofer-rate (II) ion. 

The correct answer is (C). If you remember the name of the ligand (NH3 in this case) comes first preceded by a prefix indicating the number of times the ligand occurs. This is followed by the name of the metal ion, whose charge is indicated by a Roman numeral. Finally, the name of the anion is listed. 

Many of the common metals are transition elements that have more than one possible valence. For example, tin is able to form the ions Sn2+ and Sn4+, iron can form Fe2+ and Fe3+, and copper can form Cu+ and Cu2+. (The most common transition metals with more than one valence number are listed in Table 3.3.) The name of a compound must identify which ion is present in the compound. To do this, the element s name is used, followed by the valence in parentheses, written in Roman numerals. Therefore, Sn4+ is tin(IV), Fe3+ is iron(III), and Cu2+ is copper(II). This naming method is called the Stock system after Alfred Stock, a German chemist who first used it. Some examples of Stock system names are listed in Table 3.6. 

Fig. 12. Schematic diagram of metal binding by human CCS. hCCS domains 1, 2, and 3 are labeled with roman numerals. Cysteine residues are designated as S. The disulfide bond in domain 2 is indicated by S-S. (a) Cobalt binding to hCCS. Electronic absorption spectra indicate that two equivalents of Co(II) bind per hCCS monomer, one through three or four cysteine residues in a tetrahedral geometry, and one with a geometry similar to that found in the zinc site of SODl (see text) (Zhu et al., 2000). (b) Copper binding to hCCS. XAS indicates that two Cu(I) ions bind per hCCS monomer in a sulfur-only liganding environment, with an additional heavy atom scatterer peak suggesting the presence of a /t2-bridged dicopper cluster (Eisses et al., 2000).

Naming ions of metals that form ions of more than one charge requires distinguishing between the possibilities. For example, iron forms Fe and Fe ions. We cannot call both of these iron ion because no one would know which of the two we meant. For monatomic cations of variable type, the charge in the form of a Roman numeral is attached to the element s name to indicate which ion we are talking about. For example, Fe is called iron(II) ion and Fe is called iron(lll) ion. This system of nomenclature is called the Stock system. 

Oxidation numbers are represented by Roman numerals in naming ions of metals with ions of more than one possible charge. 

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. 

Note that the use of a Roman numeral in a systematic name is required only in cases in which more than one ionic compound forms between a given pair of elements. This case most commonly occurs for compounds containing transition metals, which often form more than one cation. Elements that form only one cation do not need to be identified by a Roman numeral. Common metals that do not require Roman numerals are the Group 1A elements, which form only 1+ ions the Group 2A elements, which form only 2+ ions and aluminum, which forms only Al3+. Common transition metals that do not require a Roman numeral (because they form only one ion) are zinc (Zn2+) and silver (Ag+). 

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