Aluminum ionization potential

The nth ionization potential (IP) is the energy required to remove an electron from an atom M(n 1)+ in the gaseous state. Thus, for aluminum, we have... 

Some physical and chemical properties of aluminum are presented in Table 1. As expected for the [Ne] 3s 3p coirfiguration, the fourth ionization potential is prohibitively high. Therefore, the most common oxidation state of aluminum is three although compounds of aluminum(I) can be prepared. However, the latter species quickly disproportionate to elemental aluminum and aluminum(in) compounds. 

A major improvement was realized with the use of indium, a metal with a very low first ionization potential (5.8 eV) which works without ultrasonic radiation even at room temperature [87]. As the zero-valent indium species is regenerated by either zinc, aluminum, or tin, a catalytic amount of indium trichloride together with zinc, aluminum [88], or tin [89] could be utilized in the allylation of carbonyl compounds in aqueous medium. The regeneration of indium after its use in an allylation process could be readily carried out by electrodeposition of the metal on an aluminum cathode [90], Compared with tin-mediated allylation in ethanol-water mixtures, the indium procedure is superior in terms of reactivity and selectivity. Indium-mediated allylation of pentoses and hexoses, which were however facilitated in dilute hydrochloric acid, produced fewer by-products and were more dia-stereoselective. The reactivity and the diastereoselectivity are compatible with a chelation-controlled reaction [84, 91]. Indeed, the methodology was used to prepare 3-deoxy-D-galacto-nonulosonic acid (KDN) [92, 93], N-acetylneuraminic acid [93, 94], and analogs [95],... 

Gallium has a beautiful silvery-blue appearance it wets glass, porcelain, and most other surfaces (except quartz, graphite, and Teflon) and forms a brilliant mirror when painted onto glass. Selected physical constants of gallium are summarized in Table 1. The atomic radius and first ionization potential of gallium are almost identical with those of aluminum and the two elements frequently resemble each... 

The metal is produced on a massive scale by the Hall-Heroult method in which alumina, a non-electrolyte, is dissolved in molten cryolite and electrolyzed. The bauxite contains iron, which would contaminate the product, so the bauxite is dissolved in hot alkali, the iron oxide is removed by filtration, and the pure alumina then precipitated by acidification. Molten aluminum is tapped off from the base of the cell and oxygen evolved at the anode. The aluminum atom is much bigger than boron (the first member of group 3) and its ionization potential is not particularly high. Consequently aluminum forms positive ions AP. However, it also has non-metallic chemical properties. Thus, it is amphoteric and also has a number of covalently bonded compounds. 

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]

Fig. 179. Schematic energy-level diagram for an ITO/PPV/Al LED under forward bias, showing the ionization potential (Ip) and electron affinity (EyO of PPV, the work functions of ITO and Al (4>ito nd and the barriers to injection of electrons and holes (ISEe and A ,). There is a small barrier for hole injection from the ITO electrode into the valence band (of highest occupied molecular orbital, HOMO), and with aluminum as cathode, a considerably larger barrier for electron injection into the PPV conduction band states (of lowest unoccupied molecular orbital, LUMO). Reproduced by permission of Nature from R. H. Friend, R. W. Gymer, A. B. Holmes, J. H. Burroughes, R. N. Marks, C. Taliani, D. D. C. Bradley, D. A. Dos Santos, J. L. Bredas, M. Logdlund, and W. R. Salaneck, Nature 397,121 (1999).

As mentioned above, the operation of the device requires that electrons and holes be injected from opposite electrodes. Electrons are injected into the conduction band states of the polymer, and holes into the valence band states, and for a diode formed with a polymer such as PPV, a schematic energy level diagram as shown in Fig. 29.9 is considered appropriate. Note that there are barriers at the electrodes for injection of both electrons and holes from the aluminum and indium-tin oxide electrodes, respectively. It is difficult to make accurate predictions about the barriers to electron and hole injection (J e and respectively, in Fig. 29.9). Making reasonable assumptions about the polymer ionization potential and electrode work functions, it is clear that the barrier to injection of electrons from aluminum must be significantly larger than the barrier to injection of holes from ITO [90]. The majority of the current is therefore expected to be due to holes. Electroluminescence, however, requires the simultaneous injection of electrons, and the quantum efficiency will therefore depend strongly on the barrier to electron injection. 

Metal atoms on the metal surface, as mentioned earlier, are soft acid, and hence they combine with anions of soft base on the metal surface. Once these metal surface atoms are ionized, they form metal ions such as iron ions and aluminum ions, and the metal surface turns to be hard acid. The metal ions then combine with anions of hard base such as hydroxide ions, OH, oxide ions, 02, and sulfate ions, SO4, to form insoluble metal oxides and salts of ionic bonding character. The two-dimensional concentration of surface metal ions increases with the electrode potential of the metal, and hence the metal surface gradually becomes harder in the Lewis acidity with increasing electrode potential until it combines with anions of hard base such as oxide ions to form a metal oxide film adhering firmly to the metal surface. The passivation potential of a metal is thus regarded as a threshold potential where the metal surface grows hard enough in the Lewis acidity to combine with a hard base of oxide ions. 

Kushi and Handa (68) described in 1985 a TLC/MS method for the analysis of lipids. Secondary ion mass spectrometry with a liquid matrix of triethanolamine was used for the extraction and ionization of sample spots first located with iodine or Coomassie brilliant blue staining. A piece of TLC plate of size 5 x 20 mm could be attached to the direct insertion probe, and scanning in one-dimension was accomplished by manually inserting the probe into the source of the mass spectrometer. Spectra could be obtained from one microgram of a lipid separated on a silica TLC plate with aluminum- or plastic-backed TLC plates. Although not specifically noted in this paper, since a plastic-backed plate is an electrical insulator, some provision for connecting the surface to the plate platform itself must be made to hold the surface at the source potential. 

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