Alkali-metals

Alkali metals can donate electrons to the double bonds yielding anion radicals and positively charged, alkali-metal counterions. This may be effected either by direct attack of the monomer on the alkali metal, or by attack on the metal through an intermediate compound such as naphthalene. Both result in bifunctional initiation, that is, formation of species with two carbanionic ends. 

Alkali Metals Initiation by direct attack on the alkali metal involves transfer of the loosely held electron from a Group lA metal atom to the monomer. A radical ion (i.e., a species having both ionic and radical centers) is formed  

The initiation process thus results in a bifunctional dicarbanion species capable of propagating at both of its ends. 

Free alkali metals may be employed as solutions in certain ether solvents, in liquid arnmonia, or as fine suspensions in inert solvents. The latter are prepared by heating the metal above its melting point in the solvent, stirring vigorously to form an emulsion, and then cooling to obtain a fine dispersion of the metal. 

The alkali metals—lithium, sodium, potassium, rubidium, cesium, and francium—make up Group 1 of the periodic table. These metals are highly reactive. For example, if potassium is dropped into water, the reaction will transform potassium into potassium hydroxide and hydrogen gas. When these metals react with water, hydrogen gas is given off, and heat—often hot enough to create flames—can appear. The heat produced by the interaction is enough to liquefy the metal. 

All alkali metals are reactive, and their reactivity increases with their atomic number, or as you move from the top to the bottom of the group in the periodic table. This increase in reactivity involves the electron in the outermost shell, which gets farther away from the nucleus as you move down the metals in Group 1. The farther away this electron is from the nucleus, the less tightly it is bound to the atom. The looser this bond, the more likely the 

Two of the alkali metals, sodium and potassium, are some of the most common elements on earth. Yet, like the other alkali 

This chapter looks at various aspects of each of the alkali metals. (Notice that hydrogens location on the periodic table makes it appear as if it belongs in Group 1 with the rest of the alkali metals, even though it is actually classified as a nonmetal.) The history and other characteristics of each of these metals will be discussed. Many of the alkali metals play important roles in the environment, in technology, and in health and medicine. 

Potassium was the first alkali metal to be identified. It was discovered in 1807 by Sir Humphrey Davy (1778-1829) when he noticed the tiny molten globules that formed after he had passed an electrical current through some molten potash, a compound containing potassium and other elements such as oxygen and hydrogen. This was the first time an alkali metal had been isolated, and Davy named it potassium after the potash compound from which he isolated it. 

The alkali metals are represented by the six chemical elements of group 1A(1) of Mendeleev s periodic chart. These six elements are, in order of increasing atomic number, lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). The name alkali metals comes from the fact that they form strong alkaline hydroxides (i.e., MOH, with M = Li, Na, K, etc.) when they combine with water (i.e., strong bases capable of neutralizing acids). The only members of the alkali metal family that are relatively abundant in the Earth s crust are sodium and potassium. Among the alkali metals only lithium, sodium, and, to a lesser extent, potassium are widely used in industrial applications. Hence, only these three metals will be reviewed in detail in this chapter. Nevertheless, a short description of the main properties and industrial uses of the last three alkali metals (i.e., Rb, Cs, and Fr) will be presented at the end of the section. Some physical, mechanical, thermal, electrical, and optical properties of the five chief alkali metals (except francium, which is radioactive with a short half-life) are listed in Table 4.1. 

Properties at 298.15K (unless otherwise specified) Lithium Sodium (Natrium) Potassium (Kalium) Rubidium Cesium (Cesium) 

Wavelength maximum intensity atomic spectra line 670.8 589 766 424 460 

Standard atomic masses from Loss, R.D. (2003) Atomic weights of the elements 2001. PureAppL Chem., 75(8), 1107-1122. 

Thermodynamic properties from Chase, M.W. Jr. (1998) NIST-JANAF Thermochemical tables, 4th. ed.. Part. I II.-/. Phys. Chem. Ref. Data, Monograph No. 9, Springer, Berlin Heidelberg New York. 

The alkali metals only form monovalent ions in aqueous solution. Their low ionic charge and relatively large ionic radius lead to hydrolysis only at very high pH (near and above 14). For lithium, sodium and potassium, the ionic radii are 0.76, 1.02 and 1.38 A, respectively (Shannon, 1976). Consequently, lithium will have the strongest hydrolytic reactions due to its smaller size, but regardless all are very weak. As such, hydrolytic data are virtually only available for lithium, sodium and potassium. An upper limit for the formation of CsOH(aq) has been proposed (Baes and Mesmer, 1976), and a stability constant for this latter species has been given by Popov et al. (2002). 

Hydrdy ofMetallons, First Edition. Paul L. Brown and Christian Ekberg. 

Weighing and Introducing Metals into the Reaction Flask 

Lithium can be weighed and handled without any danger. It is usually delivered in cylindrical sticks of 1 to 1.5 cm in diameter. After complete removal of the protective liquid with a tissue, the required amount of metal is cut off and subsequently flattened with a hammer on a clean surface (e.g. iron block) to a thickness of a few mm. Using scissors, the flattened piece is then cut into chips. If a 

Lithium residues (if there are any) can be disposed by means of a 70 30 mixture of ethanol and water. 

The adsorption geometry of alkali-metal atoms on metal surfaces has been the subject of study since the earliest days of quantitative surface crystallography. Despite the apparent maturity of this field, alkali-metal adsorption is of considerable current interest. The origin of this interest is twofold. 

Prior to the early 1990s, all structural studies of alkali-metal chemisorption found the adatom located at high coordination sites at which the alkali-metal atom is bound in three- or four-fold hollow sites. A comprehensive survey of alkali-metal adsorption studies prior to 1988 may be found in the book edited by Bonzel (Bonzel et al., 1989). Several more recent LEED, SEXAFS and X-ray studies have implicated low coordination (top) sites, as in the case of Cu(lll)p(2x2)-Cs, or substitutional behavior. These results may signal that the current understanding of the alkali-metal bonding at surfaces is incomplete. 

The adsorption geometry of alkali-metal atoms chemisorbed on metal surfaces. The alkali metal to substrate bond length is derived from the determined coordinates. The adatont radius is obtained by subtracting the metallic Tadius of the substrate atom from the determined bond length. The adatom radius is expressed as the ratio of the adatom radius to the mcLallic radius of the adatom. 

Substrate Overlayer Site Adsorption height (A) M-A bond length (A) adatom radius (units of r metallic) Reference. 

Clusters of alkali metals and especially of sodium are the most studied of all. From the theoretical point of view, sodium is the one most amenable to treatments with simple models. The free-electron behavior known for the bulk phase has suggested that jellium-like models could also be suitable for small-size aggregates. By means of these models, in fact, a large variety of measurable properties have been calculated. This in turn has allowed the approximations used to be tested at several levels [121]. Two comprehensive and very instructive reviews have been dedicated to both experimental and theoretical approaches to simple metal clusters with an emphasis on phenomenological aspects and jellium or jellium-derived models [4, 5]. Here we shall report on DFT calculations that go beyond the assumption of a homogeneous, positively charged background. 

Early LSDA static pseudopotential approaches to sodium microclusters date back approximately 20 years [122], see Appendix C. It would be misleading to consider LDA calculations as the natural extension of jellium models. However, the global validity of the latter cannot but anticipate the success of the former. Clearly, these should also clarify the role of the atomic structure in determining the electronic behavior of the clusters and the extent to which the inhomogeneity of the electron distribution is reflected in the measurable properties. Many structural determinations are by now available for the smaller aggregates, made at different levels of approximation and of accuracy (e.g. [110, 111], see Appendix C). The most extensive investigation of sodium clusters so far is the LDA-CP study of Ref. [123] (see Appendix C), which makes use of all the features of the CP method. Namely, it uses dynamical SA to explore the potential-energy surface, MD to simulate clusters at different temperatures, and detailed analysis of the one-electron properties, which can be compared to the predictions of jellium-based models. 

The discussion of the one-electron properties focused on the comparison of the Kohn-Sham orbital structure with the jellium-shell model. This was done by analyzing the 

There have been many questionable attempts to study phase transformations in clusters of this size and in particular the improperly called melting . Very recently, CP-like simulations (see Appendix C) of Na4o [127] have been reported, corresponding to ultrafast 

Metal complexes with alkali metals can form according to both covalent, and non-covalent interactions between the metal center and the ligands. For these s-block elements it s common to find that the compounds are made with the metal having oxidation numbers that are lower than the metal group number. They form cluster compounds (see Chapter 15) such as RbgO, Cs,0, for example. 

Lithium is also frequently used as alkyl lithium compounds. These are useful in substitution reactions for organic chemistry and have the unique capacity to invert the polarity of the functional carbon atom. Upon reduction, it s converted from an electrophilic species to a nucleophilic species. 

This chapter deals with the organotin compounds of the Main Group metals that have usually been studied more thoroughly, and of those transition metals that have attracted more attention because the compounds find some application in organic synthesis. A more comprehensive account is given in Glockling s review.5 

Organotin compounds in which tin is bonded to an alkali metal are important reagents in synthesis, when they are usually prepared and used in situ in solution. Compounds R3SnM are known for all the alkali metals, and X-ray structures for some of the compounds Ar3SnM have been determined.10 There is also good evidence, mainly from NMR spectroscopy, for the existence in solution of 5-coordinate stannate species such as MesSn LF. 

The principal reactions by which the SnM bond can be formed are shown in equations 19-1-19-5. 

Organotin Chemistry, Second Edition. Alwyn G. Davies Copyright 2004 Wiley-VCH Verlag GmbH Co. KGaA. ISBN 3-527-31023-1 

The reactions involving the metals are usually carried out in liquid ammonia or an ether such as THF as solvent (equations 19-611 and 19-712), and can be accelerated by sonication. They involve electron transfer processes, and can also be accomplished with a metal-arene complex M Arll-, or with the metal and a trace of an arene as catalyst. The composition of the product can be determined by adding an excess of bromobenzene and analysing for PhBr and R3SnPh by GLC.12 

Lithium is used in lithium batteries because it is a light element and produces a higher battery voltage than other metals. Sodium forms a plethora of compounds used in consumer products inportant in our lives, including NaCl (table salt), NaHCOj (baking soda), and NaOH (drain cleaner, oven cleaner, soap 

Reference Stwertka, Albert, A Guide to the Elements, second edition, Oxford University Press, New York, NY 2002. 

Photolysis of phenyl-lithium in diethyl ether has been shown to give a mixture of biphenyl, ethylbenzene, phenetole, ethanol, and trace amounts of o-terphenyl. In THF the main product is biphenyl, while in the presence of pure hex-l-ene, 1-phenylhexane is produced and its quantum yield of formation has been measured, 

The historically important discovery of the specific antimanic effect of the lithium cation by the psychiatrist Cade (1949) initiated the career of this chemically simple drug as a very potent substance against symp- 

In spite of the increased medical importance of lithium during the past few decades, the main field of its application is in 

Copyright 2004 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim 

(1993). The Norton History of Chemistry. New York W. W. Norton. 

Lindsay, Jack (1970). The Origins of Alchemy in Graeco-Roman Egypt. New York Barnes and Noble. 

Alkali metals are the six elements that comprise Group I in the Periodic Table lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). Especially when dissolved in water, these elements form strong bases (alkalis) capable of reacting with and neutralizing strong acids. 

Each metal has the electron configuration of an inert (noble) gas plus one electron in the next higher s orbital. Thus, Na is or alter- 

Sodium and potassium are abundant in Earth s crust, each comprising about 2.5 percent, and the two being the 6th and 7th most abundant elements, respectively. Other alkafi metals are at least one hundred times less abundant. Francium is virtually nonexistent in the environment since all isotopes are radioactive with short half-lives. 

---

Simplest examples are prepared by the cyclic oligomerization of ethylene oxide. They act as complexing agents which solubilize alkali metal ions in non-polar solvents, complex alkaline earth cations, transition metal cations and ammonium cations, e.g. 12—crown —4 is specific for the lithium cation. Used in phase-transfer chemistry. ... 

An emulsifying agent generally produces such an emulsion that the liquid in which it is most soluble forms the external phase. Thus the alkali metal soaps and hydrophilic colloids produce O/W emulsions, oil-soluble resins the W/O type (see emulsion). 

M.p. —80°C, b.p. 37°C. Prepared from sodium azide and acid or (N2Hj) plus nitrous acid, HNO2. Heavy-metal salts, azides, are used as detonators, alkali metal salts are stable and azides are used synthetically in organic chemistry. 

Lithium chemistry Lithium is an alkali metal, electronic configuration ls 2s forming a... 

Tutton salts The isomorphous salts M2 SO4, M S04,6H20 where M is an alkali metal and M is a diposilive transition metal. 

One may rationalize emulsion type in terms of interfacial tensions. Bancroft [20] and later Clowes [21] proposed that the interfacial film of emulsion-stabilizing surfactant be regarded as duplex in nature, so that an inner and an outer interfacial tension could be discussed. On this basis, the type of emulsion formed (W/O vs. O/W) should be such that the inner surface is the one of higher surface tension. Thus sodium and other alkali metal soaps tend to stabilize O/W emulsions, and the explanation would be that, being more water- than oil-soluble, the film-water interfacial tension should be lower than the film-oil one. Conversely, with the relatively more oil-soluble metal soaps, the reverse should be true, and they should stabilize W/O emulsions, as in fact they do. An alternative statement, known as Bancroft s rule, is that the external phase will be that in which the emulsifying agent is the more soluble [20]. A related approach is discussed in Section XIV-5. 

A new dimension to acid-base systems has been developed with the use of zeolites. As illustrated in Fig. XVIII-21, the alumino-silicate faujasite has an open structure of interconnected cavities. By exchanging for alkali metal (or NH4 and then driving off ammonia), acid zeolites can be obtained whose acidity is comparable to that of sulfuric acid and having excellent catalytic properties (see Section XVIII-9D). Using spectral shifts, zeolites can be put on a relative acidity scale [195]. An important added feature is that the size of the channels and cavities, which can be controlled, gives selectivity in that only... 

A more dramatic type of restmctiiring occurs with the adsorption of alkali metals onto certain fee metal surfaces [39]. In this case, multilayer composite surfaces are fomied in which the alkali and metal atoms are intemiixed in an ordered stmcture. These stmctiires involve the substitution of alkali atoms into substrate sites, and the details of the stmctiires are found to be coverage-dependent. The stmctiires are influenced by the repulsion between the dipoles fomied by neighbouring alkali adsorbates and by the interactions of the alkalis with the substrate itself [40]. 

Tochihara H and Mizuno S 1998 Composite surface structures formed by restructuring-type adsorption of alkali-metals on FCC metals Prog. Surf. Sc/. 58 1... 

Diehl R D and McGrath R 1996 Structural studies of alkali metal adsorption and coadsorption on metal surfaces Surf. Sc/. Rep. 23 43... 

Table A2.3.2 Halide-water, alkali metal cation-water and water-water potential parameters (SPC/E model). In the SPC/E model for water, the charges on H are at 1.000 A from the Lennard-Jones centre at O. The negative charge is at the O site and the HOH angle is 109.47°.

It is also possible to explain, from hydration models, the differences between equally-charged cations, such as the alkali metals = 73,5, = 50,1 land 38.68, all in units of mor cm ). From atomic... 

Of the quantities shown in figure A2.4.8 is measurable, as is Sp, but the remainder are not and must be calculated. Values of 1-2 V have been obtained for although smaller values are found for the alkali metals. 

Recent research (1995-) has produced at very low temperatures (nanokelvins) a Bose-Einstein condensation of magnetically trapped alkali metal atoms. Measurements [41] of the fraction of molecules in the ground... 

The simplest case arises when the electronic motion can be considered in temis of just one electron for example, in hydrogen or alkali metal atoms. That electron will have various values of orbital angular momentum described by a quantum number /. It also has a spin angular momentum described by a spin quantum number s of d, and a total angular momentum which is the vector sum of orbital and spin parts with... 

Figure Bl.26.24. The change of work fimction of the (100) plane of tungsten covered by Na, K and Cs, and work fiinction of alkali metals (dashed-dotted line) versus adatom concentration n (Kiejna A and Wojciechowski 1981 Prog. Surf. Sci. 11 293-338).

One current limitation of orbital-free DFT is that since only the total density is calculated, there is no way to identify contributions from electronic states of a certain angular momentum character /. This identification is exploited in non-local pseudopotentials so that electrons of different / character see different potentials, considerably improving the quality of these pseudopotentials. The orbital-free metliods thus are limited to local pseudopotentials, connecting the quality of their results to the quality of tlie available local potentials. Good local pseudopotentials are available for the alkali metals, the alkaline earth metals and aluminium [100. 101] and methods exist for obtaining them for other atoms (see section VI.2 of [97]). 

NakatsujI H, Kuwano R, Merita H and Nakal H 1993 Dipped adcluster model and SAC-CI method applied to harpooning, chemical luminescence and electron emission in halogen chemisorption on alkali metal surface J. Mol. Catal. 82 211-28... 

Herrmann A, Leutwyler S, Schumacher E and Woste L 1978 On metal-atom clusters IV. Photoionization thresholds and multiphoton ionization spectra of alkali-metal molecules Hel. Chim. Acta 61 453... 

---