Aluminum ionic radius

The linear dependence of the pitting potential on ionic radius is likely a reflection of the similarly linear relationship between the latter and the free energy of formation of aluminum halides.108 It is reasonable to assume that the energy of adsorption of a halide on the oxide is also related to the latter. Hence, one could postulate that the potential at which active dissolution takes place is the potential at which the energy of adsorption overcomes the energy of coulombic repulsion so that the anions get adsorbed. 

The feldspars are widely distributed and comprise almost two-thirds of all igneous rocks. Orthoclase and albite (NaAlSisOg) are feldspars in which one-fourth of the silicon atoms are replaced by aluminum and anorthite (CaAl2Si20g) and has one-half of the silicon atoms replaced by aluminum. Because the ionic radius of Na+ (0.095 nm) and Ca" " (0.1 nm) are the same, solid solutions are often formed between albite and anorthite. Good stones of albite and orthoclase are known as moonstones. 

The ionic radius of aluminum in octahedral coordination is of 0.67 A. The main substituting luminescence centers are Cr " with an ionic radius of 0.75 A in octahedral coordination, Mn and Mn + with ionic radii of 0.81 and 0.67 A in octahedral coordination and and V with ionic radii of 0.93,0.78... 

Barium reacts with metal oxides and hydroxides in soil and is subsequently adsorbed onto soil particulates (Hem 1959 Rai et al. 1984). Adsorption onto metal oxides in soils and sediments probably acts as a control over the concentration of barium in natural waters (Bodek et al. 1988). Under typical environmental conditions, barium displaces other adsorbed alkaline earth metals from MnO2, SiO2, and TiO2 (Rai et al. 1984). However, barium is displaced from Al203 by other alkaline earth metals (Rai et al. 1984). The ionic radius of the barium ion in its typical valence state (Ba+) makes isomorphous substitution possible only with strontium and generally not with the other members of the alkaline earth elements (Kirkpatrick 1978). Among the other elements that occur with barium in nature, substitution is common only with potassium but not with the smaller ions of sodium, iron, manganese, aluminum, and silicon (Kirkpatrick 1978). 

Beryllium and aluminum show a similar relationship. Here, the ionic radius of aluminum (0.50 A) is considerably greater than that of beryllium (0.31 A), but the charge-per-unit-size values for the two ions are quite close since the charge ratio is 3/2. This time, in situations in which size-to-charge ratio is an important consideration, beryllium and aluminum should behave similarly. (Thus the major difficulties in the early preparation of beryllium compounds were not in their separation from their homologs but rather in their separation from the corresponding aluminum compounds.)... 

The ionic radius of aluminum (0.50 A) is 2.5 times that of boron (0.20 A), and the ionic volumes are in a ratio of about sixteen to one these ratios make it easy to understand why boron in its oxidized form exhibits behavior so much more acidic than that of trivalent aluminum and thus why boron is regarded as a typical metalloid although its congeners are metals. 

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... 

Since the ionic radius, r, is smaller for period 3 Al than for period 4 Ga, the charge density for Al is higher than for Ga and the aluminum-aqua ion is more acidic. 

For oxides, as for other minerals, a key factor controlling which cations are able to form solid solutions is the ionic radius, which must be small enough for the cations to enter octahedral sites. In this regard, it is interesting to note that Pb ", which chemisorbs strongly on aluminum hydroxide, does not readily substitute into the hydroxide during co-precipitation. This means that the rules that determine selectivity in chemisorption at a solid surface do not apply in general to substitution within the same solid. 

Only one bimetallic mechanism is presented here, as an example, the one originally proposed by Natta. He felt that chemisorptions of the organometallic compounds to transition metal halides take place during the reactions. Partially reduced forms of the di- and tri-chlorides of strongly electropositive metals with a small ionic radius (aluminum, beryllium, or magnesium) facilitate this. These chemisorptions result in formations of electron-deficient complexes between the two metals. Such complexes contain alkyl bridges similar to those present in dimeric aluminum and beryllium alkyls. The polymeric growth takes place from the aluminum-carbon bond of the bimetallic electron-deficient complexes . ... 

Indium is a member of the group 13 (formerly called IllA) elements along with boron, aluminum, gallium, and thallium. In aqueous solution, only In(lll) is stable, but compounds with I + and 2+ valences have been isolated [2], The ionic radius of In in sixfold coordination is 0.81 A in eightfold coordination, 0.92 A [3]. Although indium is not a transition metal, there are many aspects of its chemistry that resemble iron. The ionization potential, ionic radii, and coordination number of In are similar to Fe. The half-filled 3[Pg.402]

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