Beryllium and aluminium

Representative chemical properties of Be that make it diagonally related to A1 rather than vertically related to the later group 2 metals are given below. 

Further examples of similarities between the behaviours of Be and A1 can be found by comparing their reactivities (see Chapters 11 and 12). 

The following terms were introduced in this chapter. Do you know what they mean  

Fromm (2002) Crystal Engineering Communications, vol. 4, p. 318 - An article that uses structural data to consider the question of ionic versus covalent bonding in group 2 metal iodide complexes. 

Greenwood and A. Earnshaw (1997) Chemistry of the Elements, 2nd edn, Butterworth-Heinemann, Oxford -Chapter 5 gives a detailed account of the inorganic chemistry of the group 2 metals. 

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The properties of the head element of a main group in the periodic table resemble those of the second element in the next group. Discuss this diagonal relationship with particular reference to (a) lithium and magnesium, (b) beryllium and aluminium. 

Beryllium is sometimes precipitated together with aluminium hydroxide, which it resembles in many respects. Separation from aluminium (and also from iron) may be effected by means of oxine. An acetic (ethanoic) acid solution containing ammonium acetate is used the aluminium and iron are precipitated as oxinates, and the beryllium in the filtrate is then precipitated with ammonia solution. Phosphate must be absent in the initial precipitation of beryllium and aluminium hydroxides. 

It would be interesting to extend such studies to other light-atom substrates, such as the metals beryllium and aluminium, and to investigate step effects. Heavier-atom surfaces can also be analyzed in the form of thin films of mono-atomic thickness on a lighter substrate, as has recently been done ... 

Why can calcium carbide be called an acetylide, while beryllium and aluminium carbides cannot be given this name ... 

Gas chromatography has, of course, been used extensively in the analysis of many types of organic compounds with boiling points up to about 250°C, also to the analysis of organic compounds of lead, mercury, selenium, tin, manganese and silicon. Derivitisation of these compounds to produce compounds sufficiently volatile to be amenable to gas chromatography is frequently practised. Gas chromatography has also been applied to the determination of arsenic, antimony, selenium, tin, beryllium and aluminium and the common anions such as sulphate, nitrate, phosphate, sulphide, cyanide and thiocyanate. 

To 100 ml of sample 10 ml of 1M ammonium tartrate is added and the pH of the solution is adjusted to 6.0 0.5 by adding dilute ammonium hydroxide or tartaric acid solution as necessary. Transfer the solution to a 150 ml separatory funnel and add 10 ml of extractant solution. Shake for one minute then allow to stand for three to five minutes. Withdraw the organic layer and store in stoppered tubes prior to analysis. The APHA [8] use a similar extraction technique for the determination of beryllium and aluminium in water employing a nitrous oxide flame in the subsequent atomic absorption analysis, and using MIBK as a solvent. 

Another method for separating beryllium and aluminium consists of adding excess of a solution of sodium fluoride to the solution. The complex hexafluoro-aluminate, [A1F6]3 , is formed from which the metal is not precipitated as hydroxide by ammonia solution. Beryllium is, however, readily precipitated as the hydroxide under these conditions. 

D. B. Chambers, G. E. Coates, and F. Glockling Electron-impact studies on organo-beryllium and -aluminium compounds, pp. 157-164 (3). 

The i.r. (400—3700 cm ) and n.m.r. spectra of beryllium and aluminium nitrilotriacetates KBeX, HBeX,2H20, KBeX,2H20, A1X,4H20, and A1X [X = N(CH2C02)r] and their deuteriated analogues have been measured. An equilibrium ... 

Gibson s method 4 is based on the principle that ammonium hydrogen fluoride effects the complete decomposition of beryl at a low temperature, even if the mineral is only coarsely ground. Much of the silica is volatilized as ammonium fluosilicate and the beryllium and aluminium converted first to fluorides, then sulfates. The former is separated by solution in (NH COs. 

Beryllium and Aluminium borohydrides These are covalent and volatile. In these the [BH4]- groups acts as a ligand. One or more H atoms in a [BH4]- act as a bridge and bond to the metal, forming a three centre bond with two electrons. The structures are as... 

Fig. 11.05. Plan of the unit cell of the hexagonal structure of beryl, Be3Al2Si6Oi8, projected on the basal plane. The Si6018 rings (see fig. 11.03 d) at two different heights are represented as rings of shaded and unshaded tetrahedra. The beryllium and aluminium ions lie in a plane midway between the two sets of rings.

A plan of the beryl structure is shown in fig. 11.05. F°r clarity the Si04 groups are here shown as solid tetrahedra, and only the beryllium and aluminium ions are separately indicated. The Si6018 rings are clearly revealed and it will be seen that these rings are bound together... 

The window material used in vacuum cryostats is usually beryllium, aluminium, or aluminised mylar. It should be noted, however, that commercial beryllium and aluminium often contain sufficient iron to give a detectable Fe (14 keV) resonance, and this has been known to cause problems when working with this isotope. 

Pour the acidified solution into a beaker with approx. 50 ml of cold 4 m sodium hydroxide solution. Beryllium and aluminium remain in solution as beryllate and aluminate respectively, while iron, titanium and manganese are precipitated. Leave to stand for several hours, filter, collect the... 

The reaction cake is leached with water in a solid bowl type continuous centrifuge to extract the beryllium and aluminium sulphates and remove the silica. A typical analysis of the liquor is ... 

Typical examples of this class of Lewis acids are electron-deficient molecules such as the halides of boron, beryllium and aluminium, for example, BCI3, BeCl2 and AICI3. 

Optically active beryllium and aluminium alkyls have been studied as asymmetric reducing agents they appear to be considerably more effective... 

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