Periodic table electron affinity

Figure 8.1 S Trends in three atomic properties. Periodic trends are depicted as gradations in shading on miniature periodic tables, with arrows indicating the direction of general increase in a group or period. For electron affinity. Group 8A0 8) is not shown, and the dashed arrows indicate the numerous exceptions to expected trends.

Figure 6.22 I The graph shows the electron affinity (in kj/moi) vs. atomic number for the first 20 elements of the periodic table. The inset at the upper right emphasizes the general periodic trend Electron affinity increases —meaning that the value becomes more negative—from left to right and bottom to top in the periodic table.

Experimentally, electron affinity is determined by removing the additional electron from an anion. In contrast to ionization energies, however, electron affinities are difficult to measme because the anions of many elements are unstable. Table 8.3 shows the electron affinities of some representative elements and the noble gases. The overall trend is an increase in the tendency to accept electrons (electron affinity values become more positive) from left to right across a period. The electron affinities of metals are generally lower than those of nonmetals. The values vary little within a given group. The... 

Electron affinity and metallic character also exhibit periodic trends. Electron affinity is a measure of how easily an atom will accept an additional electron and is crucial to chemical bonding because bonding involves the transfer or sharing of electrons. Metallic character is important because of the high proportion of metals in the periodic table and the large role they play in our lives. Of the roughly 110 elements, 87 are metals. We examine each of these periodic properties individually in this section. 

Table 2.6 shows the electron affinities, for the addition of one electron to elements in Periods 2 and 3. Energy is evolved by many atoms when they accept electrons. In the cases in which energy is absorbed it will be noted that the new electron enters either a previously unoccupied orbital or a half-filled orbital thus in beryllium or magnesium the new electron enters the p orbital, and in nitrogen electron-pairing in the p orbitals is necessary. 

Electron affinity tends to become more negative from left to right across a row of the periodic table. 

Halogens, the elements in Group 17 of the periodic table, have the largest electron affinities of all the elements, so halogen atoms (a n readily accept electrons to produce halide anions (a a. This allows halogens to react with many metals to form binary compounds, called halides, which contain metal cations and halide anions. Examples include NaCl (chloride anion), Cap2 (fluoride anion), AgBr (bromide anion), and KI (iodide anion). 

Table 4.2 Nonrelativistic (NR) and relativistic (R) ionization potentials A p and electron affinities AEp (positive values and in eV), relativistic effects Ap and relativistic enhancement factors y for the Group 11 elements of the periodic table.

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 ... 

Several facts are apparent when the data shown in Table 1.1 are considered. In order to see some of the specific results more clearly, Figure 1.10 has been prepared to show how the electron affinity varies with position in the periodic table (and therefore orbital population). From studying Figure 1.10 and the data shown in Table 1.1, the following relationships emerge ... 

In Chapter 1 we discussed the electron affinities of atoms and how they vary with position in the periodic table. It was also mentioned that no atom accepts two electrons with a release of energy. As a result, the only value available for the energy associated with adding a second electron to O- is one calculated by some means. One way in which the energy for this process can be estimated is by making use of a thermochemical cycle such as the one that follows, showing the steps that could lead to the formation of MgO. 

In general, electron affinities become more negative from bottom to top and from left to right in the periodic table, but there are many exceptions. According to Table 5-2, the order of increasing negative values of electron affinity is ... 

The goal of this chapter is to help you relate the properties of elements to their position on the periodic table. These properties include ionization energies and electron affinities. You may want to review the basic structure of the periodic table in Chapter 2 and electron configurations in Chapter 7. And Don t forget — Practice, Practice, Practice. 

How does the effective nuclear charge affect the electron affinities of the elements in a period on the periodic table ... 

Nonmetals follow the general trends of atomic radii, ionization energy, and electron affinity. Radii increase to the left in any row and down any column on the periodic table. Ionization energies and electron affinities increase up any column and towards the right in any row on the periodic table. The noble gases do not have electron affinity values. Ionization energies are not very important for the nonmetals because they normally form anions. Variations appear whenever the nonmetal has a half-filled or filled subshell of electrons. The electronegativity... 

Sketch an outline of the periodic table and use it to compare the trends in atomic size, first ionization energy, and electron affinity. 

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