Noble metals, atomic energy levels

Theoretical analyses (75-77) of the matrix-induced changes in the optical spectra of isolated, noble-metal atoms have also been made. The spectra were studied in Ar, Kr, and Xe, and showed a pronounced, reversible-energy shift of the peaks with temperature. The authors discussed the matrix influence in terms of level shift-differences, as well as spin-orbit coupling and crystal-field effects. They concluded that an increase in the matrix temperature enhances the electronic perturbation of the entrapped atom, in contrast to earlier prejudices that the temperature dilation of the surrounding cage moves the properties of the atomic guest towards those of the free atom. 

The optical spectra of Ni, Pd and Pt in noble gas matrices have been measured in order to search for complexes of these Group VIII ligands. Changes in the energy levels of the matrix isolated atoms occur because of a weak metal interaction. For platinum the frequency shifts follow the trend Xe > Ar > Kr, but whether this interaction is described as a Van der Waals interaction or a weak coordinate bond is open to speculation.1976... 

Another way in which atoms can gain the stability of the noble gas electron configuration is by sharing the electrons in their outer energy levels. This occurs between non-metal atoms, and the bond formed is called a covalent bond. The simplest example of this type of bonding can be seen by considering the hydrogen molecule, H2. 

Figure 6.16. Comparative energy levels for magic number noble metal nanoclusters relative to bulk metal. Also shown are the perfect fee arrays of the nanoclusters, in which more than 75% of the atoms are located on the surface. Adapted with permission from Finke, R. G. in Metal Nanoparticles Synthesis, Characterization, and Applications Feldheim, D. L. Foss, C. A. eds., Dekker New York, 2002. Copyright 2002 Taylor Francis.

As members of Group 1, alkali metals have only one electron in their outer energy level. When added to water, a potassium atom gives up this electron in its outer energy level. Then, potassium will have the s and p configuration of a noble gas. 

A covalent bond forms when at least one pair of electrons is shared by two atoms. The shared electrons are found in the valence energy level and lead to a lower energy if they are shared in a way that creates a noble gas configuration (a full octet). Covalent, or molecular, bonds occur when a non-metal is bonding to a non-metal. This is due primarily to the fact that non-metals have high ionization energies and high... 

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