Binary ionic compound formula, determining

SAMPLE PROBLEM 2.6 Determining Formulas of Binary Ionic Compounds... 

Determine the formula weight in atomic mass units for each of the following binary ionic compounds ... 

Ionic compounds are named using the same guidelines used for naming binary molecules, except that the cation name aiways precedes the anion name. Thus, NH4 NO3 is ammonium nitrate, Na2 CO3 is sodium carbonate, and Ca3 (P04)2 is caicium phosphate. The subscripts are not specified in these names because the fixed ionic charges determine the cation-anion ratios unambiguously. Example 3-6 reinforces these guidelines by showing how to construct chemicai formulas from chemical names. 

The unit cell of a binary compound of copper and oxygen is shown here. Given this image and the ionic radii rc + = 0.74 A and ro>- = 1.26 A, (a) determine the empirical formula of this compound, (b) determine the coordination numbers of copper and oxygen, (c) estimate the length of the edge of the cubic unit cell, and (d) estimate the density of the compound. 

As shown in Figure 2.1, many nonmetals can have more than one oxidation number. (A more extensive list of oxidation numbers is given in Appendix Table B-15.) These numbers can sometimes be used in the same manner as ionic charges to determine formulas. Suppose, for example, you want to know the formula of a binary compound formed between sulfur and oxygen. From the common +4 and +6 oxidation states of sulfur, you could expect that sulfiu might form SO2 or SO3. Both are known compounds. Of course, a formula must represent facts. Oxidation numbers alone cannot be used to prove the existence of a compound. 

---