Electronic configurations elemental classification

These are examples of ambiguities in what may be termed secondary classification, which is not as unequivocal as primary classification, or the sequential ordering of the elements. In classical chemical terms, secondary classification corresponds to the chemical similarities between the various elements in a group. Meanwhile, in modern terms, secondary classification is explained by recourse to the concept of electronic configurations. Regardless of whether one takes a classical qualitative chemical approach or a more physical approach based on electronic configurations, secondary classification of this type is more tenuous than primary... 

The alkali metals form a homogeneous group of extremely reactive elements which illustrate well the similarities and trends to be expected from the periodic classification, as discussed in Chapter 2. Their physical and chemical properties are readily interpreted in terms of their simple electronic configuration, ns, and for this reason they have been extensively studied by the full range of experimental and theoretical techniques. Compounds of sodium and potassium have been known from ancient times and both elements are essential for animal life. They are also major items of trade, commerce and chemical industry. Lithium was first recognized as a separate element at the beginning of the nineteenth eentury but did not assume major industrial importance until about 40 y ago. Rubidium and caesium are of considerable academic interest but so far have few industrial applications. Francium, the elusive element 87, has only fleeting existence in nature due to its very short radioactive half-life, and this delayed its discovery until 1939. 

While it may be true that the periodic table is used in chemical education in order to arrive at the electronic configuration of any particular atom, this is surely not a primary goal of the periodic table for chemists in general. The main goal of the periodic table remains as the classification scheme for the properties of the elements, especially as they occur in chemical compounds.9... 

The Electronic Configurations of Atoms the Periodic Classification of the Elements... 

Extrapolation of the hem lines to Z/N = 1 defines another recognizable periodic classification of the elements, inverse to the observed arrangement at Z/N = t. The inversion is interpreted in the sense that the wave-mechanical ground-state electronic configuration of the atoms, with sublevels / < d < p < s, is the opposite of the familiar s < p < d < f. This type of inversion is known to be effected under conditions of extremely high pressure [52]. It is inferred that such pressures occur in regions of high space-time curvature, such as the interior of massive stellar objects, a plausible site for nuclear synthesis. 

Between these two blocks of elements there are two further blocks containing the transition elements. Strictly speaking, the term transition element applies to an element with a partly filled d or f subshell and so excludes those with d or d and F or electron configurations. However, it is convenient to include copper, silver and gold in this classification as these elements commonly form ions with partly filled d subshells. Although their neutral atoms have d electron configurations, it is the chemistry of their ions which is of primary interest here. Similar arguments apply to ytterbium and nobelium. Their atoms have P s ... 

Let us consider the derivation of the electron configuration of the elements from lithium to neon which constitute the second period of Men el eff s classification. The distribution of the electrons in the ground positions of the atoms is given below. In the atom of lithium, the first two electrons occupy the u position, the third electron according to the Pauli principle must fall into the electron shell having the main quantum number equal to two. The electron accordingly occupies the position of minimum energy within this shell, which is the 2s orbital. 

With die next element, chromium, however, it appears that for the first time in the construction of the periodic classification an element does not retain the electronic configuration of the previous atom. Thus in the atom of cliromium diere is only one 4s electron and five 3electronic formula for chromium is therefore... 

There are also a second and third series of transition elements, and some of the elements in these will be mentioned later. The Periodic classification is shown in Figure 8, with the electronic configurations of the elements, and the subdivisions of the K, L, and M shells are shown for convenience in table form in Figure 9. 

Understanding the distribution of chemical forms of metals within certain water types, and their uptake into biota, is based on the electronic configuration of elements and the empirical classification of electron acceptors (metals) and donors (ligands) to hard and soff categories (Morgan and Stumm 1991, Raspor 1991). The relationship between the chemical properties of elements, and their uptake and accumulation - which has implications on detoxification and food chain transfer - will be considered. Classification of trace metals as either essential (Fe, Cu, Mn, Zn, Co) or non-essential (Hg, Cd, Ag, Pb) should be performed with caution, bearing in mind that the former can exert beneficial effects at low concentrations and harmful ones at higher levels. 

C. Janet, The Helicoidal Classification of the Elements, Chemical News, 138, 372— 374, 388-393,1929 L.M. Simmons,The Display of Electronic Configuration by a Periodic Tabic, Journal of Chemical Education, 25, 658, 1948 R.T. Sanderson, A Rational Periodic Table,Joumul of Chemical Education, 41,187—189,1964 G. Katz,The Periodic Table An Eight Period Table For The 21st Centrury, The Chemical Educator, 6, 324—332, 2001 E.R. Scerri, Presenting the Left-step Periodic Table, Education in Chemistry, 42,135—136, 2005. 

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