Group III elements

Two of the material systems shown in figure G2.16.3 are of particular importance. These are the ternary compounds fonned from group III elements such as A1 and Ga in combination with As and quaternary compounds fonned from Ga and In in combination with As and P [8,15,]. Ternary Al Ga s grown on GaAs is the best known of the general class of compounds Quaternary Ga In As grown on InP is... 

Of the five Group III elements, only boron and aluminium are reasonably familiar elements. Aluminium is in fact the most abundant metal, the third most abundant element in nature, but the other elements are rare and boron is the only one so far found In concentrated deposits. 

The data in Table 7.1 show that, as expected, density, ionic radius, and atomic radius increase with increasing atomic number. However, we should also note the marked differences in m.p. and liquid range of boron compared with the other Group III elements here we have the first indication of the very large difference in properties between boron and the other elements in the group. Boron is in fact a non-metal, whilst the remaining elements are metals with closely related properties. 

Only thallium of the Group III elements is affected by air at room temperature and thalliumflll) oxide is slowly formed. All the elements, however, burn in air when strongly heated and, with the exception of gallium, form the oxide M2O3 gallium forms a mixed oxide of composition GaO. In addition to oxide formation, boron and aluminium react at high temperature with the nitrogen in the air to form nitrides (BN and AIN). 

Stability relationships among analogous molecular addition compounds of group III elements. 

Ans. (a) Pb4 + and Pb2+. (The maximum oxidation state of a group IV element and the state 2 less than the maximum.) (b) Tl3+ and Tl+. (The maximum oxidation state of a group III element and the state 2 less than the maximum.) (c) Sn4+ and Sn2+. (The maximum oxidation state of a group IV element and the state 2 less than the maximum.) (d) Cu+ and Cu2 +. (The maximum oxidation state for the coinage metals is greater than the group number.)... 

The Group III elements all have three electrons in their outer shell. Most of them form +3 ions by losing all three electrons. Because the boron atom is so small, its nucleus holds very tightly to all its five electrons. Boron usually combines with other elements which have electrons to share, just as carbon combines. It is called a semi-metal because it has some, but not all, of the metallic properties. 

Scheme 1). In these cases, the metal center formally has an even electron count and is viewed as donating a lone pair of electrons to the group III element center. Often, these L M complexes are anionic, resulting in complex ions with an overall negative charge. 

In Group III, boron, having no available d orbitals, is unable to fill its outer quantum level above eight and hence has a maximum covalency of 4. Other Group III elements, however, are able to form more than four covalent bonds, the number depending partly on the nature of the attached atoms or groups. 

A third method makes use of hydrides of group V elements together with volatile organometallic compounds of group III elements such as trimethylgallium and trimethylaluminium. 

Finally in the case of the Ga-Sb and In-Sb binaries the relative chemical potentials of the Group III element in the liquid phase have been determined experimentally. The experimental value at x = and some temperature T = T can be matched exactly using Eq. (88). The left-hand side is the experimental value so that the equation can be used to express one asymmetric interaction coefficient, say , in terms of the other, /J13. 

Tl(CH=CH2)3 n(CH3) system in detail. In this case, rapid exchange occurs, giving the mixed methylvinyl derivatives T1(CH=CH3)(CH3)2 and T1(CH=CH2)2(CH3). No T1(CH=CH2)3 was observed, and it appears that it cannot be prepared either by exchange or by direct preparative procedures. This is the only Group III element for w hich a trivinyl derivative is unknowm.1... 

Doping by group III elements allows for the substitution of Zn and thus, for the creation of one electron per dopant atom. 

Bonds to Main Group III Elements Te-B Bonds to Main Group V Elements Te—N, Te=N Bonds to Main Group VI Elements Te—O, Te—S... 

Stone, F. G. A. Stability Relationships among Adducts of Group III Elements, Chem. Revs., 58, 101 (1958). 

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