Alkali metals condensed electron

The hydrogen atom has a high ionization energy (1312kJmol ) and in this it resembles the halogens rather than the alkali metals. Removal of the Is electron leaves a bare proton which, having a radius of only about 1.5 x 10 pm, is not a stable chemical entity in the condensed phase. However, when bonded to other species it is well known in solution and in... 

When it comes to metal-rich compounds of the alkaline earth and alkali metals with their pronounced valence electron deficiencies it is no surprise that both principles play a dominant role. In addition, there is no capability for bonding of a ligand shell around the cluster cores. The discrete and condensed clusters of group 1 and 2 metals therefore are bare, a fact which leads to extended inter-cluster bonding and results in electronic delocalization and metallic properties for all known compounds. 

Ammonia is a colorless, pungent-smelling gas, consisting of polar, trigonal pyramidal NH3 molecules that have a lone pair of electrons on the N atom. Because of hydrogen bonding (Section 10.2), gaseous NH3 is extremely soluble in water and is easily condensed to liquid NH3, which boils at —33°C. Like water, liquid ammonia is an excellent solvent for ionic compounds. It also dissolves alkali metals, as mentioned in Section 6.7. 

Intercalation of cations into a framework of titanium dioxide is a process of wide interest. This is due to the electrochromic properties associated with the process (a clear blue coloration results from the intercalation) and to the system s charge storage capabilities (facilitated by the reversibility of the process) and thus the potential application in rocking-chair batteries. We have studied alkali-metal intercalation and ion diffusion in the Ti02 anatase and spinel crystals by theoretical methods ranging from condensed-phase ab initio to semiempirical computations [65, 66]. Structure relaxation, electron-density distribution, electron transfer, diffusion paths and activation energies of the ion intercalation process were modeled. 

In 1958, Pitzer (141), in a remarkable contribution that appears to have been the first theoretical consideration of this phenomenon, likened the liquid-liquid phase separation in metal-ammonia solutions to the vapor-liquid condensation that accompanies the cooling of a nonideal alkali metal vapor in the gas phase. Thus, in sodium-ammonia solutions below 231 K we would have a phase separation into an insulating vapor (corresponding to matrix-bound, localized excess electrons) and a metallic (matrix-bound) liquid metal. This suggestion of a "matrix-bound analog of the critical liquid-vapor separation in pure metals preceeded almost all of the experimental investigations (41, 77, 91,92) into dense, metallic vapors formed by an expansion of the metallic liquid up to supercritical conditions. It was also in advance of the possible fundamental connection between this type of critical phenomenon and the NM-M transition, as pointed out by Mott (125) and Krumhansl (112) in the early 1960s. 

The electrons ejected from molecules by the passage of ionizing radiation through condensed media can be solvated very soon after the primary ionizing event and the solvated electron, e q, so formed can undergo chemical reactions with solute and solvent molecules. The main evidence for the existence of solvated electrons in the liquid phase has been obtained by the use of pulse radiolysis in conjunction with optical spectroscopy (Hart and Boag, 1962). Very recently the e.s.r. spectrum of the solvated electron has been obtained by a similar method (Avery et ah, 1968). The solvated electron is not located on one solvent molecule but is associated with an assembly of molecules which form a potential well around the electron by virtue of dipolar and polarization forces. There is a close similarity between this system and the blue solutions obtained by dissolving alkali metals in liquid ammonia. 

The sodium condensation reaction of a,co-bis(chlorosilyl)-substituted compounds and the coupling reaction of dilithio derivatives of compounds bearing 7t-electron systems with dichlorosilanes offer a convenient route to various silicon containing polymers. However, the polymers prepared by these methods always contain a small proportion of siloxy units in the polymer backbone, which would interrapt the electron delocalisation. Therefore, new synthetic routes to organosilicon polymers have been developed in which no alkali metal halide condensations are involved [6, 7]. We report syntheses of organosilicon... 

When alkali metal atoms are co-condensed with strong electron acceptors in matrices, electron transfer occurs spontaneously, as discussed above in the case of K + O3. If not spontaneous, electron transfer can easily be activated by photolysis. Irradiation by the Nao line (583 nm cf. ionization energy corresponding to 243 kJmol ) is sufficient to transfer the sodium valence electron to several molecular substrates e.g., CI2 CI2, B2H6 B2Hft, HI -> H + I. ... 

An interesting variation is initiation by a combination of an alkali metal and an aromatic with condensed rings, e.g., naphthalene. The aromatic anion radical transfers an electron to a monomer such as styrene, which then dimerizes and grows at both ends [66,76],... 

In the first two parts of this chapter, electron transfer (ET) from atomic donors, e.g., alkali metals or the iodine anion, to an accepting unit composed of simple molecular or atomic solvents was discussed. It was demonstrated that even for a molecule without a stable anionic state or large dipole moment, e.g., water and ammonia, an ensemble of a relatively small number of the molecules can act as an electron acceptor. In the case of the solvated alkali metal atom clusters, ET takes place spontaneously as the number of solvent molecules increases, while the ET in the solvated 1 clusters is induced by photoexcitation into the diffuse electronic excited states just below the vertical detachment thresholds. These ET processes in isolated supermolecular systems resemble the charge delocalization phenomena in condensed phases, e.g., excess-electron ejection from alkali metals into polar solvents and the charge transfer to solvent in a solution of stable anions. 

The best known and most studied systems in which the formation of solvated electrons is observed are the alkali metal — liquid ammonia systems. Shortly after his discovery of alkali metals, Davy initiated studies into their reactions with dry gaseous anunonia. In November 1808 he noticed that potassium assumed a beautiful metallic appearance and gradually became of a fine blue colour when heated in an ammonia atmosphere. It is today difficult to interpret the processes that occured in his experiment. Most probably, he noticed a form of the electron localized in a condensed phase. Unfortunately, this and other analogous records of Davy remained unknown for long only in 1980 were they discovered and later published... 

In Group IA(1), lithium and sodium have the condensed electron configuration [noble gas] ns (where n is the quantum number of the outermost energy level), as do all the other alkali metals (K, Rb, Cs, Fr). All are highly reactive metals that form ionic compounds with nonmetals with formulas such as MCI, M2O, and M2S (where M represents the alkali metal), and all react vigorously with water to displace H2. 

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