Aluminum oxide electron configurations

All aluminum nuclei have charge +13 electronic units, so that 13 electrons orbit the nucleus of the neutral atom. Its electronic configuration can be abbreviated as an inner core of inert neon (a noble gas) plus three more electrons (Ne)3s23p1, which locates Al in Group IIIA of the chemical periodic table, between boron (B) and gallium (Ga). Its principal oxidation state is +3, so its oxide is A1203, a very important compound in cosmochemistry. Its chloride is A1C13. 

There is also a pronounced tendency for the Group IIIA metals to form metal-metal bonds and bridged structures. The electron configuration ns2 np1 suggests the possible loss of one electron from the valence shell to leave the ns2 pair intact. The electron pair that remains in the valence shell is sometimes referred to as an inert pair, and a stable oxidation state that is less than the group number by two units is known as an inert pair effect. The fact that oxidation states of +2, +3, +4, and +5 occur for the elements in Groups IVA, VA, VIA, VIIA, respectively, shows that the effect is quite common. Thus, it will be seen that the Group IIIA metals other than aluminum have a tendency to form +1 compounds, especially thallium. 

The alkaline earth metals are somewhat less electropositive and less reactive than the alkali metals. Except for the first member of the family, beryllium, which resembles aluminum (a Group 3A metal) in some respects, the alkaline earth metals have similar chemical properties. Because their ions attain the stable electron configuration of the preceding noble gas, the oxidation number of alkaline earth metals in the combined form is almost always +2. Table 20.5 lists some common properties of these metals. Radium is not included in the table because all radium isotopes are radioactive and it is difficult and expensive to study the chemistry of this Group 2A element. 

Electron tunneling spectroscopy applied in a different experimental configuration can yield the vibrational structure of adsorbates. For example, by adsorbing a monolayer of molecules at an aluminum oxide-lead interface, the vibrational spectrum of benzoic acid was obtained by plotting d V/dP, the second derivative of the applied voltage with respect to the tunnel current, versus the applied voltage V. The result is shown in Figure 5.19. The experiment was performed at 4.2 K. 

Next, consider aluminum oxide, the whitish coating that forms on aluminum chairs. To acquire a noble-gas configuration, each aluminum atom loses three electrons and each oxygen atom gains two electrons. Thus, three oxygen atoms are needed to accept the six electrons lost by two aluminum atoms. The neutral compound formed is aluminum oxide (AI2O3). 

The Group 3A elements have the ns np outer electron configuration. Aluminum shows only the -E3 oxidation state in its compounds. The heavier metals (Ga, In, Tl) can lose or... 

Fig. 4.9 Energies of free cations and of ionic compounds as a function of the oxidation state of the cation. Top Lines represent the ionization energy necessary to form the +1. +2, +3, and + 4 cations of sodium, magnesium, and aluminum. Note that although the ionization energy increases most sharply when a noble gas configuration is broken, isolated cations are always less stable in Itiifher oxidation states. Bottom Lines represent the sum of ionization energy and ionic bonding energy for hypothetical molecules MX, MXj, MXj, and MX in which the interatomic distance, r, has been arbitrarily set at 200 pm. Note that the most stable compounds (identified by arrows) arc NaX, MgXj, and AlXj. (All of the.se molecules will be stabilized additionally to a small extent by the electron affinity of X.)...

As mentioned earlier, PPV was the first polymer used in a PLED. The device architecture of this PLED is shown in Figure 5.1. The EL polymer, PPV in this case, was sandwiched between a transparent conductor, indium tin oxide (ITO), as the anode and aluminum as the cathode. In this configuration, when a voltage is applied to the electrodes, holes are injected into the HOMO of the PPV at the ITO-PPV interface and electrons are injected into the LUMO of the PPV at the Al-PPV interface. These... 

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