Atomic properties periodic trends

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.

Electron Configurations, Atomic Properties, and Periodic Trends... 

An element s tendency towards partitioning into solid phases is related to its fundamental atomic properties. These properties follow periodic trends, giving rise to the trends shown in Figure 11.5 for the oceanic residence times of the elements. In the broadest sense, these trends reflect the relative tendency of an element towards electrostatic versus covalent interactions. Chemists have devised various measures of this tendency, such as an element s electronegativity and its ionization potential. The latter is a predictor of electrostatic interactions and is defined as the ratio, z /r, where... 

Two chemists in attendance at the Karlsruhe were Julius Lothar Meyer (1830-1895) and Dmitri Mendeleev (1834-1907). These two independently developed the periodic law and constructed their own versions of the periodic table. Meyer based his table primarily on the physical properties of the elements. Meyer plotted atomic volume against the atomic mass and noticed the periodicity in volumes of the elements. Other physical properties also showed periodic trends. Figure 6.2 shows how the melting point of the first fifty-five elements rises and falls in a roughly periodic fashion as atomic number increases. Based on his analysis, Meyer published his periodic table in 1870. 

The periodic trend of a decrease in atomic radii across a period is readily seen in the Figure 6.4. Other properties related to atomic radii show a similar pattern. Knowing that the elements exhibit a general periodic trend allows us to predict unknown properties for elements and aided in the discovery of unknown elements. The periodic nature of the elements supported the development of the quantum theory. The elements show a periodic pattern in both their properties and electron configurations. The periodic trend in properties of the elements... 

A Brief Summary of Atomic Theory, the Basis of the Periodic Table and Some Trends in Atomic Properties... 

The semimetals, or metalloids, are known to exhibit some of the properties of metals and some of those of nonmetals. The semimetals are B, Si, Ge, As, Sb, Te, and At. They are highlighted in bold in the partial periodic table in Figure 4.1. The elements located to the left of the semimetals are the metals those to the right of the semimetals are the nonmetals. Identifying an element as a metal, nonmetal, or semimetal is important in identifying periodic trends and in identifying the types of bonds that atoms will form with each other. 

Chemistry is primarily concerned not with the properties of single molecules but with periodic trends, homologous series and the like. It is, therefore, important that any method which we apply to the problem of molecular electronic structure depends linearly on the number of electrons in the system being studied. Meaningful comparisons of atoms and molecules of different sizes are then possible. This property has been termed size-consistency1-2. Independent electron models, such as the widely used Hartree-Fock approximation, provide a size-consistent theory of atomic and molecular structure. 

The ionization radii calculated for all atoms with this procedure show remarkable periodicity that mirrors many trends observed or inferred empirically for atomic properties such as electronegativity, covalent radii etc. Also indicated is a simple explanation for promotion of atoms into their valence state, before a chemical reaction commences [114]. This generally accepted mechanism, never satisfactorily explained before, can be accounted for simply in terms of environmental pressure. Whenever an atom is crowded because of high pressure or temperature or even concentration on a catalytic surface, the valence electron becomes promoted towards its ionization limit. In this limit the atom enters the valence state as an electron becomes decoupled from... 

Since so much can be predicted or at least rationalized on the basis of the periodicity of a few simple atomic properties, especially Pauling electronegativity, size, and charge (or oxidation number) see Oxidation Number) of the atoms or ions involved, we begin by looking at these trends in some detail (beyond that done in General Chemistry courses) and... 

We have developed a fairly complete picture of polyelectronic atoms that is quite successful in accounting for the periodic table of elements. We will next use the model to account for the observed trends in several important atomic properties ionization energy, electron affinity, and atomic size. 

In this section we have seen that the trends in atomic properties summarized by the periodic table can be a great help in understanding the chemical behavior of the elements. This fact will be emphasized over and over as we proceed in our study of chemistry. 

What atomic property affects periodic trends down a group in the periodic table ... 

What two atomic properties have an increasing trend as you move across a period ... 

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