Names of Ionic Compounds

The most challenging ion combination occurs when one ion has a charge of 3 and the other a charge of 2. The lowest common multiple is 6, so to obtain balance you must have two ions with a charge of 3 and three ions with a charge of 2. The next example illustrates this with both monatomic and polyatomic ions. 

Co to http //now.brookscole.com/ cracoliceJe and click Coached Problems for a simulation on Predicting Ionic Compound Formulas. 

Write the formulas of aluminum oxide and barium phosphate. 

Start with aluminum oxide. Remember, you need two 3s and three 2s. 

The ions are Al and 0 . Two Al + ions and three 0 ions give a charge balance of 2 X (3+) -F 3 X (2—) = 0 with the least number of each ion. If you wrote Al40g, you have the charge balanced, but you did not do it with the fewest number of ions possible. Both 4 and 6 are divisible by 2 to give AI2O3. 

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. 

Exerdse For the compounds listed below, where x and y are unspecified subscripts, give the compound formula and name. 

Answers (a) KCl, potassium chloride (b) KjS, potassium sulfide (c) AIF3, aluminum fluoride (d) LiCl, lithium chloride (e) LiF, lithium fluoride (f) LijO, lithium oxide, (g) K3N, potassium nitride (h) Ca3N2, calcium nitride (i) Mg3Nj, magnesium nitride 0) MgO, magnesium oxide (k) CaO, calcium oxide (1) CaS, calcium sulfide. 

Compound Formula Compound Name Neutral Compound Formed from the Ions Below 

M2O3 Aluminum oxide l vo +3 ions and three -2 ions 

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D.1 Names of Cations D.2 Names of Anions D.3 Names of Ionic Compounds D.4 Names of Inorganic Molecular Compounds D.5 Names of Some Common Organic Compounds... 

Now that we know how to name the cations and anions, we merely have to put the two names together to get the names of ionic compounds. The cation is named first and the anion is named next. The number of cations and anions per formula unit need not be included in the name of the compound because anions have characteristic charges, and the charge on the cation has already been established by its name. There are as many cations and anions as needed to get a neutral compound with the lowest possible subscripts. 

How do we name nonionic (covalent) compounds If a pair of elements forms only one compound, begin with the name of the element that appears first in the chemical formula, followed by the second element, with the suffix -ide added to its root. This is analogous to the naming of ionic compounds. Just as NaBr is sodium bromide, so the following names designate typical covalent compounds ... 

In each case, we identify the chemical formulas of the ions from Table 2-3. These ions must be present in the simplest whole-number ratio that gives the compound no net charge. Recall that the formulas and names of ionic compounds are written by giving the positively charged ion first. 

Formulas and Names of Ionic Compounds Interpreting Formulas... 

The names of ionic compounds consist of the name for the cation followed by the name for the anion. Tables 3.7 and 3.8 summarize the ways cations and anions are named. 

Although many compounds are molecular (as presented in Chapter 2), a very large number are best described as ionic, those composed of ions. In this chapter, the focus is on the formulas and names of ionic compounds. Nearly all ionic compounds are composed of both metals and nonmetals. Remember that metals have a great tendency to lose electrons in chemical reactions to form positive ions (cations), while nonmetals, in their reaction with metals, have a great tendency to gain electrons to form negative ions (anions). These ions of opposite charge combine to form ionic compounds. 

It is important to remember that numerical prefixes are not used in the names of ionic compounds. It would be incorrect to name (NH4)3P04 triammonium phosphate. The only time you would see a numerical prefix is if it is part of the name of a polyatomic ion, as in the d/hydrogenphosphate ion. 

Writing Names of Ionic Compounds from the Formuia of the Compound... 

Names of ionic compounds are derived from the names of their ions. The name of the cation appears first, followed by the name of the anion. In the Stock system for naming an ion (the systematic name), a Roman numeral indicates the charge of the cation. In the older common nomenclature system, the suffix -ous indicates the lower of the ionic charges, and the suffix -ic indicates the higher ionic charge. 

Names of ionic compounds consist of the cation name followed by the anion name ... 

WRITING FORMULAS FROM NAMES OF IONIC COMPOUNDS 103... 

Writing Formulas from Names of Ionic Compounds... 

Names of ionic compounds follow the form cation name + anion name, without reference to how many of each ion are present. 

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. ... 

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