Atomic properties electron affinity

Three atomic properties—atomic size, ionization energy (energy involved in removing an electron from an atom), and electron affinity (energy involved in adding an electron to an atom)—exhibit recurring trends throughout the periodic table. 

The formation of Na from Na and Cl from CI2 indicates that an electron has been lost by a sodium atom and gained by a chlorine atom—we can envision an electron transfer from the Na atom to the Cl atom. Two of the atomic properties discussed in Chapter 7 give us an indication of how readily electron transfer occurs ionization energy, which indicates how easily an electron can be removed from an atom, and electron affinity, which measures how much an atom wants to gain an electron. = (Sections 7.4... 

Several portions of Section 4, Properties of Atoms, Radicals, and Bonds, have been significantly enlarged. For example, the entries under Ionization Energy of Molecular and Radical Species now number 740 and have an additional column with the enthalpy of formation of the ions. Likewise, the table on Electron Affinities of the Elements, Molecules, and Radicals now contains about 225 entries. The Table of Nuclides has material on additional radionuclides, their radiations, and the neutron capture cross sections. 

All the elements in a main group have in common a characteristic valence electron configuration. The electron configuration controls the valence of the element (the number of bonds that it can form) and affects its chemical and physical properties. Five atomic properties are principally responsible for the characteristic properties of each element atomic radius, ionization energy, electron affinity, electronegativity, and polarizability. All five properties are related to trends in the effective nuclear charge experienced by the valence electrons and their distance from the nucleus. 

Electronegativity measures how strongly an atom attracts the electrons in a chemical bond. This property of an atom involved in a bond is related to but distinct from ionization energy and electron affinity. As described in Chapter 8, ionization energy measures how strongly an atom attracts one of its own electrons. Electron affinity specifies how strongly an atom attracts a free electron. Figure 9 6 provides a visual summary of these three... 

Schwerdtfeger, P. (1991) Relativistic and Electron Correlation Contributions in Atomic and Molecular Properties. Benchmark Calculations on Au and Au2. Chemical Physics Letters, 183, 457 163. Neogrady, P., Kello, V., Urban, M. and Sadlej, A.J. (1997) Ionization Potentials and Electron Affinities of Cu, Ag, and Au Electron Correlation and Relativistic Effects. International Journal of Quantum Chemistry, 63, 557-565. 

The Periodic Table forms one of the most remarkable, concise, and valuable tabulations of data in science. Its power lies in the regularities that it reveals, thus, in some respects, it has the same role as the SOM. Construct a SOM in which the input consists of a few properties of some elements, such as electronegativity, atomic mass, atomic radius, and electron affinity. Does the completed map show the kind of clustering of elements that you would expect What is the effect of varying the weight given to the different molecular properties that you are using ... 

As is the case with ionization potential, the electron affinity is a useful property when considering the chemical behavior of atoms, especially when describing ionic bonding, which involves electron transfer. 

Pauling based electronegativity values on bond energies between atoms, but that is not the only way to approach the problem of the ability of atoms in a molecule to attract electrons. For example, the ease of removing an electron from an atom, the ionization potential, is related to its ability to attract electrons to itself. The electron affinity also gives a measure of the ability of an atom to hold on to an electron that it has gained. These atomic properties should therefore be related to the ability of an atom in a molecule to attract electrons. Therefore, it is natural to make use of these properties in an equation... 

As we have seen, several atomic properties are important when considering the energies associated with crystal formation. Ionization potentials and heats of sublimation for the metals, electron affinities, and dissociation energies for the nonmetals, and heats of formation of alkali halides are shown in Tables 7.1 and 7.2. 

It is surprisingly difficult to find reliable values of I and E a). Probably the most extensive collection of data is Bond Energies, Ionization Potentials and Electron Affinities by V. I. Vedeneyev, V. L. Gurvich, V. N. Kondrat yev, Y. A. Medvedev and Ye. L. Frankevich, Edward Arnold, London, 1966. The Chem Guide Website has several good pages, e.g. look at http //www.chemguide.co.uk/atoms/properties/eas.html. 

One surprising physical property of fluorine is its electron affinity which, at — 333 kJmol is lower than that of chlorine, —364 kJmol-1, indicating that the reaction X(g) + e - X (g) is more exothermic for chlorine atoms. In view of the greater reactivity of fluorine a much higher electron affinity might reasonably have been expected. The explanation of this anomaly is found when the steps involved in a complete reaction are considered. For example, with a Group I metal ion M+(g) the steps to form a crystalline solid are,... 

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