Electronic structures of ions

Absorption of electromagnetic radiation in the visible and ultraviolet regions of the spectrum resulting in changes in the electronic structure of ions and molecules. 

The concept of molecular orbitals (MOs) helps to explain the electron structure of ion-radicals. When one electron abandons the highest occupied molecular orbital (HOMO), a cation radical is formed. HOMO is a bonding orbital. If one electron is introduced externally, it takes the lowest unoccupied molecular orbital (LUMO), and the molecule becomes an anion-radical. LUMO is an antibonding orbital. Depending on the HOMO or LUMO involved in the redox reaction, organic donors appear as n, a, or n species, whereas organic acceptors can be tt or a species. Sometimes, a combination of these functions takes place. 

Our next task is to decide on the likely binary formulas of the ionic compounds that may be formed by metals and nonmetals. The key lies in the electronic structures of ions. 

The concept of molecular orbital helps explain the electron structure of ion radicals. When one electron abandons the highest occupied molecular orbital (HOMO), a cation radical is formed. If one electron is introduced externally, it takes up the lowest unoccupied molecular orbital (LUMO), and the molecule becomes an anion radical. 

Connection Between Ion Radical Reactivity and Electron Structure of Ion Radical Products... 

Lawley KP, Donovan RJ. 1993. Spectroscopy and electronic structure of ion-pair states . Faraday Trans. 89(12) 1885-1898. 

Iditional importance is that the vibrational modes are dependent upon the reciprocal e vector k. As with calculations of the electronic structure of periodic lattices these cal-ions are usually performed by selecting a suitable set of points from within the Brillouin. For periodic solids it is necessary to take this periodicity into account the effect on the id-derivative matrix is that each element x] needs to be multiplied by the phase factor k-r y). A phonon dispersion curve indicates how the phonon frequencies vary over tlie luin zone, an example being shown in Figure 5.37. The phonon density of states is ariation in the number of frequencies as a function of frequency. A purely transverse ition is one where the displacement of the atoms is perpendicular to the direction of on of the wave in a pmely longitudinal vibration tlie atomic displacements are in the ition of the wave motion. Such motions can be observed in simple systems (e.g. those contain just one or two atoms per unit cell) but for general three-dimensional lattices of the vibrations are a mixture of transverse and longitudinal motions, the exceptions... 

In TT-complexes formed from aromatic compounds and halogens, the halogen is not bound to any single carbon atom but to the 7r-electron structure of the aromatic, though the precise geometry of the complexes is uncertain. The complexes with silver ions also do not have the silver associated with a particular carbon atom of the aromatic ring, as is shown by the structure of the complex from benzene and silver perchlorate. ... 

The characteristic lines observed in the absorption (and emission) spectra of nearly isolated atoms and ions due to transitions between quantum levels are extremely sharp. As a result, their wavelengths (photon energies) can be determined with great accuracy. The lines are characteristic of a particular atom or ion and can be used for identification purposes. Molecular spectra, while usually less sharp than atomic spectra, are also relatively sharp. Positions of spectral lines can be determined with sufficient accuracy to verify the electronic structure of the molecules. 

The ground-state electronic structure of As, as with all Group 15 elements features 3 unpaired electrons ns np there is a substantial electron affinity for the acquisition of 1 electron but further additions must be effected against considerable coulombic repulsion, and the formation of As is highly endothermic. Consistent with this there are no ionic compounds containing the arsenide ion and... 

The Spectra and Electronic Structure of the Tetrahedral Ions Mn04, Cr04 and C104 ... 

Complex ions used for electroplating are anions. The cathode tends to repel them, and their transport is entirely by diffusion. Conversely, the field near the cathode assists cation transport. Complex cyanides deserve some elaboration in view of their commercial importance. It is improbable that those used are covalent co-ordination compounds, and the covalent bond breaks too slowly to accommodate the speed of electrode reactions. The electronic structure of the cyanide ion is ... 

In Sec. 2 it was pointed out that, when studying ions in a vacuum, we are mainly interested in the electronic structure of each species of ion but in dilute solution the center of interest is largely shifted to the little... 

This model of the electronic structure of complex ions explains why high-spin and low-spin complexes occur only with ions that have four to seven electrons (d4, d5, d6, d7). With three or fewer electrons, only one distribution is possible the same is true with eight or more electrons. 

Lewis structure An electronic structure of a molecule or ion in which electrons are shown by dashes or dots (electron pairs), 166-167,192q formal charge, 171-172 nonmetal oxides, 564-565 oxoacids, 567 resonance forms, 170-171 writing, 168-169 Libby, Willard, 174... 

Another feature in PES spectra is the so-called shake-up structures, appearing as weak satellites on the high binding energy side of the main line. The shake-up structure reflects the spectrum of the 1 -electron-2-hole states generated in connection with pholoionization, and can give useful information about the valence n-electronic structure of a molecular ion. 

As we saw in Chapter 19, chlorine represents the other extreme in chemical reactivity. Its most obvious chemical characteristic is its ability to acquire electrons to form negative chloride ions, and, in the process, to oxidize some other substance. Since the tendency to lose or gain electrons is a result of the details of the electronic structure of the atom, let us try to explain the chemistry of the third-row elements on this basis. 

The change in the electronic structure of a bulk metal catalyst, in consequence of its transformation into the hydride, influences respectively the metal surface atoms (ions) or, strictly speaking, their d orbitals. Recent achievements and the present knowledge of the subject only permit us so far to formulate such general conclusions. 

The most information on the electronic structure of Pu ions is available for Pu(IV) compounds. As far as our own results are... 

It should be emphasized that whereas the theoretical modelling of An3+ spectra in the condensed phase has reached a high degree of sophistication, the type of modelling of electronic structure of the (IV) and higher-valent actinides discussed here is restricted to very basic interactions and is in an initial state of development. The use of independent experimental methods for establishing the symmetry character of observed transitions is essential to further theoretical interpretation just as it was in the trivalent ion case. 

Each equivalent atom (the same element, the same number of bonds and lone pairs) has the same formal charge. A check on the calculated formal charges is that their sum is equal to the overall charge of the molecule or ion. For an electrically neutral molecule, the sum of the formal charges is zero. Compare the formal charges of each possible structure. The structure with the lowest formal charges represents the least disturbance of the electronic structures of the atoms and is the most plausible (lowest energy) structure. 

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