Ionic compounds aluminum oxide example

An ionic compound typically contains a multitude of ions grouped together in a highly ordered three-dimensional array. In sodium chloride, for example, each sodium ion is surrounded by six chloride ions and each chloride ion is surrounded by six sodium ions (Figure 6.11). Overall there is one sodium ion for each chloride ion, but there are no identifiable sodium-chloride pairs. Such an orderly array of ions is known as an ionic crystal. On the atomic level, the crystalline structure of sodium chloride is cubic, which is why macroscopic crystals of table salt are also cubic. Smash a large cubic sodium chloride crystal with a hammer, and what do you get Smaller cubic sodium chloride crystals Similarly, the crystalline structures of other ionic compounds, such as calcium fluoride and aluminum oxide, are a consequence of how the ions pack together. 

What about when the ionic charges aren t equal to each other The most mathematically sophisticated way to determine this ratio is to seek the least common multiple between the absolute values of the charges on the cation and anion. Most beginning students, however, simply use the criss-cross method, as shown in Figure 2.9. That is, the number of cations in the formula is the absolute value of the charge on the anion. The number of anions in the formula is the absolute value of the charge on the cation. For example, as shown above, the formula of the ionic compound containing aluminum ions and oxide ions is... 

In Chapter 5, we learned to write formulas for ionic compounds from the charges on the ions and to recognize the ions from the formulas of the compounds. For example, we know that aluminum chloride is AICI3 and that VCI2 contains ions. We cannot make comparable deductions for covalent compounds because they have no ions there are no charges to balance. To make similar predictions for species with covalent bonds, we need to use the concept of oxidation number, also called oxidation state. A system with some arbitrary rules allows us to predict formulas for covalent compounds from the positions of the elements in the periodic table and also to balance equations for complicated oxidation-reduction reactions. 

In combination reactions, two substances, either elements or compounds, react to produce a single compotmd. One type of combination reaction involves two elements. Most metals react with most nonmetals to form ionic compounds. The products can be predicted from the charges expected for cations of the metal and anions of the nonmetal. For example, the product of the reaction between aluminum and bromine can be predicted from the following charges 3-1- for aluminum ion and 1— for bromide ion. Since there is a change in the oxidation numbers of the elements, this type of reaction is an oxidation-reduction reaction ... 

For the monomer to be dispersible in the suspension system, it must be immiscible or fairly insoluble in the reaction medium. In some instances, partially polymerized monomers or prepolymers are used to decrease the solubility and also increase the particle size of the monomer. The initiators employed in the polymerization reaction are mainly of the peroxide type and, in some cases, are azo and ionic compounds. Examples include benzoyl, diacetyl, lauroyl, and /-butyl-peroxides. Azo-bis-isobutyronitrile (AIBN) is one of the most frequently used azo initiators, while aluminum and antimory alkyls, titanium chloride, and chromium oxides are typical ionic initiators. The amount of catalyst used depends on the reactivity of the monomer and the degree of polymerization, varying from 0.1 to 0.5% of the weight of the monomer. 

Precious and semiprecious gemstones are examples of ionic compounds called minerals that are cut and polished to make jewelry. For example, sapphires and rubies are made of aluminum oxide, AI2O3. Impurities of chromium make rubies red, and iron and titanium make sapphires blue. 

Corrosion can also occur by a direct chemical reaction of a metal with its environment such as the formation of a volatile oxide or compounds, the dissolution of metals in fused metal halides. The reaction of molybdenum with oxygen and the reaction of iron or aluminum with chlorine are typical examples of metal/gas chemical reactions. In these reactions, the metal surface stays film-free and there is no transport of electrical charge.1 Fontana and Staehle2 have stated that corrosion should include the reaction of metals, glasses, ionic solids, polymeric solids and composites with environments that embrace liquid metals, gases, aqueous and other nonaqueous solutions. 

Thallium has two important oxidation states, Tl (-El) and Tl (+3). The trivalent form more closely resembles aluminum and the monovalent form more resembles alkali metals such as potassium. The toxic nature of the monovalent Tl is due to its similarity to potassium in ionic radius and electrical charge. Thallium sulfate use as a pesticide was restricted in 1965 in the USA and the World Health Organization (WHO) recommended in 1973 against its use as a rodenticide due to its toxicity (WHO, 1973). From 1912 to 1930, thallium compounds were used extensively for medicinal purposes for example in the treatment of ringworm (because of the depilatory effects), dysentery, and... 

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