Other Types of Ionic Crystals

Other Types of Ionic Crystals.—In the preceding sections we have been talking about simple binary crystals, formed from a positive and a negative ion of the same valency. Of course, there are many other types of ionic crystals, and we shall not take up the other sorts in nearly such detail. We shall, however, list a number of crystal structures, with the 

In Table XXIII-8 we give the crystals that exist in the fluorite structure and the distances between nearest neighbors. In addition, we tabulate the sum of the ionic radii of Table XXIII-2. Though these were computed from binary compounds of elements of equal valency, they 

In addition to the fluorite structure, there are a number of other structures assumed by similar compounds. We shall not attempt to enumerate or describe them. Some of them are considerably more complicated than the fluorite structure, but they resemble it in that there is no semblance of separate molecules. Each positive ion is surrounded by a number of negative ions and each negative by a number of positives, at equal distances, so that it is in no sense correct to say that one ion is Fio. xxiii-o.—Tho rairite struc-bound to one or two neighbors more than ture  

Substance C-0 distance, angstroms C-metal distance O-metal distance 

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IONIC CRYSTAL. A crystal ihut consists effectively of ions bound lugclher by Iheir electrostatic attraction. Examples of such crystals are the alkali halides, including potassium fluoride, potassium chloride, potassium bromide, potassium iodide, sodium fluoride, and the other combinations of sodium, cesium, rubidium or lithium ions with fluoride, chloride, bromide or iodide ions. Many other types of ionic crystals are known,... 

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