Selenium ionization energy

Selenium, ionization energy, 410 Self oxidation-reduction, 361 Separation of charge, 312 Separations by crystallization, 413 by distillation, 70 by precipitation, 176 Seventh column of periodic table, 352... 

On the basis of your knowledge of periodicity, place each of the following sets of elements in order of decreasing ionization energy. Explain your choices, (a) Selenium, oxygen, tellurium (b) gold, tantalum, osmium (c) lead, barium, cesium. 

Arrange the following atoms in order of increasing first ionization energy oxygen, tellurium, selenium. 

The group of the chalcogens sulfur, selenium and tellurium is a typical triad of the more electronegative nonmetals with relatively high-ionization energies, relatively strong element-element bonds and a clear tendency to form mono-and polyatomic anions (Table 1). 

The photoelectron spectrum of 2,1,3-benzoselenadiazole (1), 2,1,3-benzothiadiazole and their tetrafluoro derivatives were measured. Replacement of sulfur by selenium did not appreciably alter the 7t molecular-orbital ionization energies <91KGS563). 

There has been a great deal of interest in recent years in photoelectron spectroscopy (PES) of the isomeric A,B-diheteropentalenes containing sulfur, selenium and nitrogen. This technique has offered for the first time direct experimental evaluation of the ionization energies of the valence electrons. The sulfur- and selenium-containing heteroaromatics appear to be the class most investigated by PES. The ionization potentials of various A,B-diheteropentalenes, are presented in Table 3. 

The highest occupied molecular orbital (HOMO) in formaldehyde and heteroaldehydes, H2C=E, is the lone pair at E (nE), and the second highest MO (SOMO) is the C=E 77-bonding orbital. The LUMO is the 77 CE orbital composed of the antibonding combination of pz(C) and pz(E). The ionization energy of the HOMO in formaldehyde is 10.88 eV and of the SOMO 14.5 eV, as determined by photoelectron spectroscopy.33 The ionization energy of the HOMO and the SOMO both decrease considerably when the oxygen atom in formaldehyde is replaced by sulfur or selenium (see Fig. 1, data are compiled from Refs. 33-37). 

Ionization energy generally increases from left to right across a row of the periodic table and decreases from top to bottom down a group. Chlorine should have a larger E than its neighbor sulfur, and selenium should have a smaller E than sulfur. 

Consider the elements selenium (Se) and bromine (Br). Which has the higher first ionization energy Which has the higher electron affinity ... 

Photoelectron spectroscopy has demonstrated that there is no linear correlation between the ionization energies and p values of azoles <84JHC269>. The gas phase photoelectron spectra of a series of hydantoin derivatives (32) have been compared with those of model compounds, and with the results of HAM/3 and CNDO/S calculations. Evidence is found for significant interactions between the 7r-orbitals and the chalcogen atoms for sulfur and selenium derivatives. In contrast, n-orbitals of the nitrogen atoms are localized in the whole series of compoimds, especially in the oxy analogues and in monosubstituted derivatives <88JST(175)447>. 

Among the metalloids, iodine can be introduced in appreciable amounts (up to 17 at.%) into glassy arsenic selenide and it also forms bonds that are essentially covalent in nature. The iodine atoms are incorporated in selenium chains and rings forming bond terminations of the type. .. Se-I. The Se-Se and I-Se bonds have comparable ionization energies [4]. For this reason iodine does not have an appreciable effect on the electrical conductivity of arsenic selenide. It merely eliminates the blocking of carriers by the chains and rings of excess selenium and thereby renders continuous conduction possible [5]. The formation of chain terminations when iodine is introduced into arsenic selenide reduces the chemical stability of the latter. 

Vydyanath and co-workers [8.80] have reported the development of selenium-doped Si for 3-5 pm detection selenium acts as a donor. The ionization energy of selenium was found from photoconductivity measurements to be 0.3 eV, corresponding to = 4.1 pm, They found the maximum solubility of selenium in Si to be slightly under 10 atoms/cm. ... 

The internal photoelectric effect, just as infrared radiation, was also first observed in the 19th century, when certain minerals such as selenium or lead sulfide were found to increase their electrical conductivity in the presence of light. These photoconductors depend upon the photoexcitation of bound electrons and/or holes into the conduction and/or valence bands of the material. Then, at the turn of the century, external photoemission was discovered in vacuum diodes. As first explained by Einstein, the photoelectric effect was found to have a threshold wavelength determined by the relation hv = he lk>E, where E is the energy required for the electron to exit the material. In the case of a semiconductor, the excitation energy, E, is that of the gap between the valence and conduction bands or the ionization energy of an impurity in the material. The electronic detector family has two main branches, the first being the vacuum photodiode and its more useful... 

This behaviour is explained by moderate values of first ionization energy, electronegativity, electron affinity and atomic radius. Non-metallic oxides are often acidic and react with water. So the oxides of selenium, Se02 and Se03, are expected to react with water to form acidic solutions of H2Se03 and H2Se04. 

The alkali metals as well as selenium lie near the boundary between the classes. As an average, class 1.2 contains lighter elements having high ionization energies, more electrons in the last shell, a stronger trend toward negative oxidation states, and a smaller affinity for chlorine. In class 1.1, but near the boundary of class 1.2, are situated As, Cd, and Na. 

Some physical constants for selenium are given in Table 1. More extensive data and many sources are available (1 5). For a selenium atom, the covalent radius is ca 0.115 nm, the electron affinity for two electrons is ca —2.33 eV, ie, energy absorbed, and the first ionization potential is 9.75 eV. 

The values of the energy states of gaseous monatomic selenium are taken from McLennan and Crawford.1 Gibbs and Ruddy1 reported a value for the ionization potential. The spectra of Se+ (g) have not been analyzed, but the higher spectra are discussed by Rao6 and Sawyer and Humphreys.1 See also Bacher and Goudsmit.1... 

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