Roman numeral, in naming

Roman numerals in names denote charges on ions Arabic numerals in formulas tell the number of atoms or ions present per formula unit. 

I Roman numerals in names stand for charges, and subscripts in formulas represent numbers of atoms. 

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

In each case, identify the cations and their charges, based on periodic table group numbers or on oxidation states appearing as Roman numerals in names Ba, Ca, and Fe. Then identify the anions and their charges 0 , F, and Combine the cations and anions in the relative numbers required to produce electrically neutral formula units. 

There is one complication. As mentioned earlier, certain metals in the transition and post-transition series form more than one cation, for example, Fe2+ and Fe3+. To distinguish between these cations, the charge must be indicated in the name. This is done by putting the charge as a Roman numeral in parentheses after the name of the metal ... 

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. 

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). 

Name compounds by applying the guidelines. The guidelines for naming binary compounds that contain metals differ from those for compounds containing no metal. Unless a metal forms only one stable atomic cation, its charge must be specified with a Roman numeral in parentheses. 

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... 

After the ligands are named, the name of the metal is given next, with its oxidation state indicated by Roman numerals in parentheses with no spaces between the name of the metal and the parentheses. 

A The name of each of these ionic compounds is the name of the cation followed by that of the anion. Each anion name is a modified (with the ending ide ) version of the name of the element. Each cation name is the name of the metal, with the oxidation state appended in Roman numerals in parentheses if there is more than one type of cation for that metal. 

The periodic table arranges the elements in a way that shows many of their properties and relationships to each other.The horizontal rows are called periods, and the vertical columns are called groups.The groups, numbered 1 through 18, are Hsted at the top of each column right underneath in parentheses are former Roman numeral group names I through Vlll that are sometimes still used. Each element is represented by a letter symbol, with the fuU name printed at the top. The atomic number, which is the number of proto ns in the nucleus, is written above each element. 

For transition metal compounds, the charge on the cation is indicated by the Roman numeral in the name. Knowing the number of positive charges, you can then figure out the number of necessary negative charges for the associated anions. 

Use a Roman numeral in parentheses, immediately following the name of the metal, to indicate the metal s oxidation state. As shown by the preceding examples, there is no space between the name of the metal and the parenthesis. 

Some elements, such as copper and iron, possess two ions with different valencies. Copper can form the Cu+ ion and the Cu2+ ion, with valencies 1 and 2 respectively. Therefore it can form two different compounds with chlorine, CuCl and CuCl2. We can also distinguish the difference by using Roman numerals in their names CuCl is copper(i) chloride and CuCl2 is copper(n) chloride. Similarly, iron forms the Fe2+ and Fe3+ ions and so can also form two different compounds with, for example, chlorine FeCl2 (iron(n) chloride) andFeCl3 (iron(m) chloride). 

If the transition metal forms only one cation, you name it like a representative metal cation name the element and call it a cation. If the transition metal forms more than one cation, you need to name the metal and then indicate the charge on the cation with Roman numerals in parentheses. 

Headings are alphabeted straight through, letter by letter, as in Chemical Abstracts indexes, not word by word. Roman numerals in Stock names are ignored in alphabeting unless two or more names are otherwise the same. 

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. 

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 ... 

In CU2S, the two copper ions are balanced by one sulfide ion with a 2 charge the charge on each copper ion must be 1 +. In CuS, only one copper ion is present to balance the 2- charge on the sulfide ion the charge on the copper ion is 2 +. Note that the Roman numerals in the names of monatomic cations denote the charges on the ions. The Arabic numerals appearing as subscripts in formulas denote the number of atoms of that element present per formula unit. Either of these numbers can be used to deduce the other, but they are not the same ... 

To name an ionic compound, name the cation first and then the anion. Use just the name of the element for monatomic cations of elements that form only one cation. For monatomic cations of elements that can form more than one cation, indicated the charge on the cation by a Roman numeral in parentheses added to the name of the element. Polyatomic cations have special names, ammonium ion being the most important. 

A Roman numeral in parentheses in the name of the compound designates the charge on a cation and an Arabic numeral as a subscript in the formula designates the number of atoms or ions. The charges enable us to deduce the numbers of ions, and vice versa, but the Roman numerals and the Arabic numerals do not represent the same quantities. (Section 6.2)... 

Oxidation numbers are used in the Stock system for naming compounds. Positive oxidation numbers are denoted as Roman numerals in parentheses in the names of the compounds the numbers of atoms or ions can be deduced from the oxidation numbers. (In contrast, the subscripts in formulas give the numbers of atoms or ions, from which the oxidation numbers may be deduced.) (Section 16.2). 

Stock system (6.2, 16.2) The nomenclature system for inorganic compounds in which the oxidation state (or charge for a monatomic cation) is represented as a Roman numeral in the name of the compound, stoichiometry (10.1) The determination of how much a reactant can produce or how much of a product can be produced from a given quantity of another substance in a reaction. 

Ans. (a) CU2S and (b) CuS. Nofe carefully that the Roman numerals in the names mean one thing—the charge on the ion—and the Arabic numeral subscripts in the formulas mean another—number of atoms. Here the copper(I) has a charge of 1 +, and therefore two copper(I) ions are required to balance the 2— charge on one sulfide ion. The copper(II) ion has a charge of 2+, and therefore one such ion is sufficient to balance the 2— charge on the sulfide ion. 

Ans. (a) Copper(II) oxide (b) copper(I) oxide. This example again emphasizes the difference between the Arabic numerals in a formula and the Roman numerals in a name. 

A compound containing a metal that forms multiple cations must have a Roman numeral in its name. 

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+). 

---