Ionic compounds common ions from

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. 

In Sections 4.2 and 4.3 we encountered two types of chemical reactions that can occur when two electrolyte solutions are combined precipitation, in which ionic compounds exchange ions, and acid-base neutralization, in which a proton is transferred from an acid to a base. In this section, we will learn about oxidation-reduction reactions, commonly called redox reactions. A redox reaction is a chemical reaction in which electrons are transferred from one reactant to another. For example, if we place a piece of zinc metal into a solution that contains copper ions, the following reaction will occur ... 

Precipitation involves the alteration of the ionic equilibrium to produce insoluble precipitates. To remove the sediment, chemical precipitation is allied with solids separation processes such as filtration. Undesirable metal ions and anions are commonly removed from waste streams by converting them to an insoluble form. The process is sometimes preceded by chemical reduction of the metal ions to a form that can be precipitated more easily. Chemical equilibrium can be affected by a variety of means to change the solubility of certain compounds. For e.xample, precipitation can be induced by alkaline agents, sulfides, sulfates, and carbonates. Precipitation with chemicals is a common waste stream treatment process and is effective and reliable. The treatment of sludges is covered next. 

The principal product of the reaction of the alkali metals with oxygen varies systematically down the group (Fig. 14.15). Ionic compounds formed from cations and anions of similar radius are commonly found to he more stable than those formed from ions with markedly different radii. Such is the case here. Lithium forms mainly the oxide, Li20. Sodium, which has a larger cation, forms predominantly the very pale yellow sodium peroxide, Na202. Potassium, with an even bigger cation, forms mainly the superoxide, K02, which contains the superoxide ion, O,. ... 

An enormous amount of chemistry is carried out in solutions that consist of ionic compounds that have been dissolved in a solvent. In order to separate the ions from the lattice in which they are held, there must be strong forces of interaction between the ions and the molecules of the solvent. The most common solvent for ionic compounds is water, and that solvent will be assumed for the purposes of this discussion. 

Writing the formula for ionic compounds requires us to know the charge of the cation and anion making up the ionic compound. Information on the charge of common ions can be obtained from the periodic table. More will be said about this in Chapter 7, but for now, a few basic rules will help us write the formulas for simple ionic compounds ... 

A sodium ion and a chloride ion together make the chemical compound sodium chloride, commonly known as table salt. This and all other chemical compounds containing ions are referred to as ionic compounds. All ionic compounds are completely different from the elements from which they are made. 

Sodium chloride, or common salt , is water-soluble, as are most other ionic compounds. Because the solution contains a charged set of ions, it will conduct electricity. Such electrically conducting solutions are generally called electrolytes . Electrolytes are solutions containing ions which can freely move around. The ions are attracted to areas or electrodes of opposite charge. They are repelled from areas... 

Apart from complexes such as the alkoxides, dialkylamides, and organo compounds discussed in later sections, all of the Mg—Ra elements give ionic compounds in the solid state and in solutions. They form salts with common anions like the halides, NOj, RC02, CIO4, SO ", and so on. Because of its smaller size Mg2+ is the hardest of the ions. While Mg2+ and Ca2+ salts are usually hydrated, those of Sr, Ba, and Ra are commonly anhydrous. The coordination number for Mg2+ is almost invariably 6 but a few cases of 5, 7, and 8 coordination are known.20 The... 

The driving force behind double substitution reactions is the formation of a covalent compound (including water or a gaseous compound) or an insoluble ionic compound from ions in solution. A solid formed from ions in solution is called a precipitate. We can thus predict that a reaction will occur if soluble ionic compounds yield at least one insoluble ionic compound or one covalent compound. We need to be familiar with the solubilities of some common ionic compounds in water. Some types of ionic compounds that are soluble or insoluble in water are listed in Table 8.3. A more comprehensive tabulation of solubilities is presented in Table 8.4 for reference, not necessarily to be memorized. 

The ionic compound formed from the caicium ion and the phosphate ion is a common ingredient in fertiiizers. Write the formuia for this compound. 

A binary Ionic compound is one composed of ions from only two elements, one a metal, the other a nonmetal. NaCl, CaF2, and FeCl3 are all binary ionic compounds. Before starting to develop formulas for ionic compounds, it is necessary to know the monatomic ions (ions formed from a single atom) of the common metals and nonmetals. 

Up to this point, only ions derived from single atoms have been used since the focus has been on binary ionic compounds. But there are many ions, almost all of them anions, that contain two or more atoms, and they are the polyatomic ions. Polyatomic ions contain two or more atoms chemically bound into a single unit that bears an electrical charge. The most common polyatomic ions are listed in the following table. 

As mentioned above, X-ray structures only give a precise knowledge of the distances between the atoms. While this is not so important for pure metals, as the interatomic distance is simply divided by two to obtain the metallic radius, this simple method will not work for ionic compounds. To begin, it is assumed that the individual ions are spherical and in contact. The strategy then used to derive ionic radii is to take the radius of one commonly occurring ion, such as the oxide ion, O2-, as a standard. Other consistent radii can then be derived by subtracting the standard radius from measured inter-ionic distances. 

It is less expensive than ion exchange because there is no cost for regeneration of the resin. The practical maximums are about 8% for the ionic concentration and about 40% for nonionics. It is easily automated. The biggest disadvantage is that the resin and the solution must have common cations or anions, which usually limits the ionic species to a single contaminant. Ion exclusion works backward, in that the major component of a mixture is removed when separating ionic compounds from nonionic compounds. 

Compounds Formed from Polyatomic Ions Ionic compounds in which one or both of the ions are polyatomic are very common. Table 2.5 gives the formulas and the names of some common polyatomic ions. Remember that the polyatomic ion stays together as a charged unit. The formula for potassium nitrate is KNO3 each balances one N03. The formula for sodium carbonate is Na2C03 two Na balance one CO-. When two or more of the same polyatomic ion are... 

As an approximation, the dissolved portion of a slightly soluble salt dissociates completely into ions. In a saturated solution, the ions are in equilibrium with the solid, and the product of the ion concentrations, each raised to the power of its subscript in the compound s formula, has a constant value (Qsp = K p). The value of K p can be obtained from the solubility, and vice versa. Adding a common ion lowers an ionic compound s solubility. Adding HgO" (lowering the pH) increases a compound s solubility if the anion of the compound is that of a weak acid. If Qsp > K p for an ionic compound, a precipitate forms when two solutions, each containing one of the compound s ions, are mixed. Lakes bounded by limestone-rich soils form buffer systems that prevent harmful acidification by acid rain. 

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