Likewise because there are three oxygen ions the

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Likewise, because there are three oxygen ions, the total anion charge is three times the charge on each oxygen ion. total cation charge + total anion charge = 0 2x + 3( 2) = 0 x = + 3 The iron ions must be + 3 in order for them to balance the 6 from three 2 oxide ions, so the cation name is iron(III). Because O 2 is a monatomic anion, its name includes the root of the name of the nonmetal and ‑ide. Therefore, Fe 2 O 3 is iron(III) oxide . O BJECTIVE 37 E XERCISE 3.8 - N AMING I ONIC C OMPOUNDS Write the names that correspond to the following formulas: (a) LiCl (used in soft drinks to help reduce the escape of bubbles), (b) Cr 2 (SO 4 ) 3 (used in chrome plating), and (c) NH 4 HCO 3 (used as a leavening agent for cookies, crackers, and cream puffs). O BJECTIVE 37 CoCl 2 is used to make vitamin B-12. 106 Chapter 3 Chemical Compounds
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3.5 Ionic Compounds 107 Converting Names of Ionic Compounds to Formulas Before you can write a chemical formula from the name of a compound, you need to recognize what type of compound the name represents. For binary ionic compounds, the first part of the name is the name of a metallic cation. This may include a Roman numeral in parentheses. The anion name starts with the root of the name of a nonmetal and ends with ‑ide . (name of metal)(maybe Roman numeral) (root of nonmetal)ide For example, aluminum fluoride (used in the production of aluminum) and tin(II) chloride (used in galvanizing tin) are binary ionic compounds. You can identify other names as representing ionic compounds by recognizing that they contain the names of common polyatomic ions. For example, ammonium chloride and iron(III) hydroxide are both ionic compounds. Many of the polyatomic ions that you will be expected to recognize end in ‑ate , so this ending tells you that the name represents an ionic compound. Copper(II) sulfate is an ionic compound. Follow these steps to write formulas for ionic compounds. Step 1 Write the formula, including the charge, for the cation. (See Figure 3.17 to review the charges on monatomic cations.) Step 2 Write the formula, including the charge, for the anion. (See Figure 3.17 to review the charges on monatomic anions. See Table 3.6 to review polyatomic ion formulas.) Step 3 Write subscripts for each formula so as to yield an uncharged compound. Table 3.9 shows examples. Use the lowest whole number ratio for the subscripts. If the subscript for a polyatomic ion is higher than one, place the formula for the polyatomic ion in parentheses and put the subscript outside the parentheses. Ionic charges General formula Example ions Example formula X + and Y XY Na + and Cl NaCl X + and Y 2 X 2 Y NH 4 + and SO 4 2 (NH 4 ) 2 SO 4 X + and Y 3 X 3 Y Li + and PO 4 3 Li 3 PO 4 X 2 + and Y XY 2 Mg 2 + and NO 3 Mg(NO 3 ) 2 X 2 + and Y 2 XY Ca 2 + and CO 3 2 CaCO 3 X 2 + and Y 3 X 3 Y 2 Ba 2 + and N 3 Ba 3 N 2 X 3 + and Y XY 3 Al 3 + and F AlF 3 X 3 + and Y 2 X 2 Y 3 Sc 3 + and S 2 Sc 2 S 3 X 3 + and Y 3 XY Fe 3 + and PO 4 3 FePO 4 Table 3.9 Possible Cation-Anion Ratios (X represents the cation, and Y represents the anion.)
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  • Fall '06
  • Mark
  • Atom, atoms, Chemical bond

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