Copper electron affinity

Table 5. Photoelectrical work function

The enthalpy of atomization of copper does not differ at all for the two compounds, and the atomization of chlorine adds only a small difference for the second mole of chlorine. The major energy cost for CuCl2 is the second ionization energy of copper which is compensated by the electron affinity to form the second chloride ion and especially the lattice energy. Since the electron ionized to form Cu2 is a d electron and does not break a noble gas structure, IE2 is not excessive, and both CuCl and CuCl2 are stable compounds. 

The energy with which electrons are bound in conducting materials is known as the electron affinity of the material. Materials with a high electron affinity bind electrons strongly and exhibit noble behavior (i.e., are relatively inert and do not oxidize spontaneously in air). Gold is an example. On the other hand, metals such as aluminum or copper are less noble and their surfaces, once exposed to air, are readily oxidized. When two dissimilar electronic conductors are placed in contact with each other, electrons flow from the material that is less noble (e.g., copper) to the more noble material (e.g., palladium) until an equilibrium is reached and the contact potential is formed at their junction. Because of the multitude of possible combinations of conductors in the real world, contact potential is the most ubiquitous of all junction potentials. 

Let us make a simple electrical circuit from palladium and copper. First the ends of the two metals are arranged in such a way that they form a parallel plate capacitor (Fig. 6.29). An electric field appears between the two plates, which is the result of the spontaneous separation of electrons, driven by the difference of their electron affinities. 

The small affinities of lithium and sodium are of little importance, but copper, silver and gold, with completed d shells, possess marked electron affinity and whereas the alkaline earth metals, with completed s levels, have negative electron affinities, mercury, with a completed d and s level, has a high positive electron affinity. 

Fig. 6. Comparison between the spheroidal jellium model (Penzar and Ekard [43]) and experiment [45,46] for the electron affinity of Copper clusters as a function of the number of atoms N...

The later work was mostly done by physicists, who generally favoured the contact theory, but Lodge, while criticising Ostwald and Nernst, favoured the view that the electrification of metals on contact is due to the oxidation of one of them. No earlier experimenter succeeded in removing air and moisture effectively from the apparatus. When this was done, the results favoured the contact theory. A metal has an electron affinity related to the work of removal of an electron from it in a vacuum. If two metals are put in contact, electrons pass from one to the other and the potential difference 1- 2 between them is equal to the Volta contact potential. For zinc < 2 = 3 4 for copper 1 = 4 0, hence - 2 = 0 6, which is of the order of the measured contact potential. The influence of ion concentration in the solution on the electrode potential has not been very successfully accounted for. Chalmers thought the chemical theory explained the facts as well as the contact theory. 

New problems on explaining trends in electron affinities on the basis of radial distribution functions, the reaction between aqueous copper chloride solution and aluminum metal, assigning structural classes to simple boranes, isomers of carboranes, and semitopological diagrams for alanes... 

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