Compounds ternary ionic

414 6 octahedron 3 triangle rutile MgF2, FeF2, ZnF2, Si OP, Sn02, Ru02 

When the positions of cations and anions are interchanged, the same structure types result for the CsCl, NaCl and zinc blende type. In the case of the fluorite type the interchange also involves an interchange of the coordination numbers, i.e. the anions obtain coordination number 8 and the cations 4. This structure type sometimes is called anti-fluorite type it is known for the alkali metal oxides (Li20. Rb20). 

The structure types discussed so far have a favorable arrangement of cations and anions and are well suited for ionic compounds consisting of spherical ions. However, their occurrence is by no means restricted to ionic compounds. The majority of their representatives are found among compounds with considerable covalent bonding and among intermetallic compounds. 

Several additional, more complicated structure types are known for ionic compounds. For example, according to the radius ratio, one could expect the rutile type for strontium iodide (rSr2+ /i = 0.54). In fact, the structure consists of Sr2+ ions with a coordination number of 7 and anions having two different coordination numbers, 3 and 4. 

When three different kinds of spherical ions are present, their relative sizes are also an important factor that controls the stability of a structure. The PbFCl type is an example having anions packed with different densities according to their sizes. As shown in Fig. 7.5, the Cl- ions form a layer with a square pattern. On top of that there is a layer of F ions, also with a square pattern, but rotated through 45°. The F ions are situated above the edges of the squares of the Cl- layer (dotted line in Fig. 7.5). With this arrangement the F -F distances are smaller by a factor of 0.707 (= /2) than the CP-CP distances this matches the ionic radius ratio of rF-/rcl- = 0.73. An F layer contains twice as many ions as a CP layer. Every Pb2+ ion is located in an antiprism having as vertices four F and four 

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An antisite defect is an atom on an inappropriate site in a crystal, that is, a site normally occupied by a different chemical species. In a compound of formula AB the antisite defects that can occur are an A atom on a site normally occupied by a B atom, or a B atom on a site normally occupied by an A atom. Antisite defects are not very important in binary ionic compounds, as the misplacement of an ion is energetically costly, and so unfavorable. In ternary ionic compounds, however, such as spinels, AB204, the transfer of A ions to B sites and vice versa, is not... 

Ionic compounds consist of positive ions (cations) and negative ions (anions) hence, ionic compounds often consist of a metal and nonmetal. The electrostatic attraction between a cation and anion results in an ionic bond that results in compound formation. Binary ionic compounds form from two elements. Sodium chloride (NaCl) and sodium fluoride (NaF) are examples of binary ionic compounds. Three elements can form ternary ionic compounds. Ternary compounds result when polyatomic ions such as carbonate (C032 ), hydroxide (OH-), ammonium (NH4+), form compounds. For example, a calcium ion, Ca2+, combines with the carbonate ion to form the ternary ionic compound calcium carbonate, CaC03. Molecular compounds form discrete molecular units and often consist of a combination of two nonmetals. Compounds such as water (H20), carbon dioxide (C02), and nitric oxide (NO) represent simple binary molecular compounds. Ternary molecular compounds contain three elements. Glucose ( 12 ) is a ternary molecular compound. There are several distinct differences between ionic and molecular compounds, as summarized in Table 1.2. 

The first thing to point out is the charge on tin. While tin has more than one possible charge, you know it has to be two in this case because of the Roman numeral (II) that appears in the name. The formula Sn202 does not represent the smallest ratio of ions. You should notice that if each one of these subscripts is reduced by the new formula will be SnO. You can only reduce these subscripts if all subscripts in a formula can be reduced by the same amount (this will be more critical with ternary ionic compounds). 

Ternary ionic compounds are ionic compounds containing one or more polyatomic ions. The possible combinations are a monatomic cation bonded to a polyatomic anion, a polyatomic cation bonded to a monatomic anion, or a polyatomic cation bonded to a polyatomic anion. There are additional rules that must be added to the rules in the previous section ... 

When the ternary ionic compound that we are trying to name contains a cation (positive ion) with multiple oxidation states, we still need to employ the stock system. For example, if we were asked to name the compound with the formula Cu(N03)2, we would determine that the oxidation number of the copper must be +2, because there are two nitrate ions, each with a charge of -1, and +2 + 2(-l) = 0. This would give us the name copper (II) nitrate for this compound. 

Compounds that contain three elements are classed as ternary compounds. Most of the ionic compounds that contain a polyatomic ion, such as Na2S04, are ternary ionic compounds. 

Use the two ions to construct a correct formula for a ternary ionic compound. 

Possible Types of Defect Pairs in Ternary Ionic Compounds... 

The compounds described in Example 10-2 are binaty ionic compounds consisting of monatomic cations and monatomic anions. Commonly encountered ternary ionic compounds consist of monatomic and polyatomic ions. Bonding between atoms within the polyatomic ions is covalent. Some ternary ionic compounds are considered later in the chapter. 

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