Periodic classification of the elements

The transition metals are the elements in Groups IB and 3B through 8B, which have incompletely fiUed d subshells, or readily produce cations with incompletely 

Ireshomi ground-state electron configurations of the elements. For simplicity, oniy the configurations of the outer electrons 

The chemical reactivity of the elements is largely determined by their valence electrons, which are the outermost electrons. For the representative elements, the valence electrons are those in the highest occupied n shell. All nonvalence electrons in an atom are referred to as core electrons. Looking at the electron configurations 

For the representative elements, the valence electrons are simply those electrons at the N est principal energy level n. 

1 lA Representative elements Noble gases Transition metals Zinc Cadmium Mercury 18 8A 

A modern periodic table usually shows the atomic number along with the element symbol. As you already know, the atomic number also indicates the number of electrons in the atoms of an element. Election configurations of elements help explain the recurrence of physical and chemical properties. The importance and usefulness of the periodic table lie in the fact that we can use om understanding of the general properties and trends within a group or a period to predict with considerable accuracy the properties of any element, even though that element may be unfamiliar to us. 

An atom of a certain element has 15 electrons. Without consulting a periodic table, answer the following questions (a) What is the ground-state electron configuration of the element (b) How should the element be classified (c) Is the element diamagnetic or paramagnetic  

Solution (a) We know that for = 1 we have a G orbital (2 electrons) for = 2 we have a Is orbital (2 electrons) and three 2p orbitals (6 electrons) for = 3 we have a is orbital (2 electrons). The number of electrons left is 15 12 = 3 and 

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

The chemistry of an element is determined by the manner in which its electrons are arranged in the atom. Such arrangements are the basis of the modern periodic classification of the elements the Periodic Table. 

The treatment of atoms with more than one electron (polyelectronic atoms) requires consideration of the effects of interelectronic repulsion, orbital penetration towards the nucleus, nuclear shielding, and an extra quantum number (the spin quantum number) which specifies the intrinsic energy of the electron in any orbital. The restriction on numbers of atomic orbitals and the number of electrons that they can contain leads to a discussion of the Pauli exclusion principle, Hund s rules and the aufbau principle. All these considerations are necessary to allow the construction of the modern form of the periodic classification of the elements. 

From a chemical point of view the most important result is that number theory predicts two alternative periodic classifications of the elements. One of these agrees with experimental observation and the other with a wave-mechanical model of the atom. The subtle differences must be ascribed to a constructionist error that neglects the role of the environment in the wave-mechanical analysis. It is inferred that the wave-mechanical model applies in empty space Z/N = 0.58), compared to the result, observed in curved non-empty space, (Z/N = t). The fundamental difference between the two situations reduces to a difference in space-time curvature. 

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. 

These metals constitute the left-hand or A families in Groups I and II of the periodic classification of the elements, as shown in the table inside the back cover of the book. 

PERIODIC CLASSIFICATION OF THE ELEMENTS ACCORDING TO THEIR ATOMIC NUMBERS AND THE ARRANGEMENT OF THEIR ELECTRONS... 

MendeMeff had made many enemies by his espousal of liberal movements. In 1880, the St. Petersburg Academy of Sciences refused, in spite of very strong recommendations, to elect him member of its chemical section. His liberal tendencies were an abomination. But other and greater honors came to this sage. The University of Moscow promptly made him one of its honorary members. The Royal Society of England presented him with the Davy Medal which he shared with Lothar Meyer for the Periodic Classification of the Elements. 

The new theories that spring from the application of Bohmian mechanics to chemical problems reveal a close connection between chemical phenomena and the attributes of space-time. The most fundamental principle of chemistry is the periodic classification of the elements in terms of natural numbers. Examined against the background of number theory a deeper level of periodicity that embraces all nuclides is revealed and found to relate on a cosmic scale to an involution in space-time structure. 

Table IX Periodic Classification of the Elements expanded form)...

Now for the real genius part he said that an element would eventually be discovered which would have a RAM and properties that would mean that it fitted into the gap he had left. He even predicted its properties the properties of an element that had never been seen by anyone. Only a few years later an element was discovered and given the name germanium (Ge). When its RAM was measured, it fitted exactly between gallium and arsenic. When its other properties were studied, it was found that they fitted Mendeleev s predictions with amazing accuracy (he had predicted its density to within three decimal places, for example). This and other predictions were sufficient to convince other scientists of the validity of the periodic classification of the elements, but there were still a few anomalies to be sorted out, which were not fully appreciated until 1932 when the neutron was discovered. 

Figure II-l Standard order of arrangement of the elements and compounds based on the periodic classification of the elements (from Ref [82WAG/EVA])...

The periodic classification of the elements is derived directly on the basis of Pauli s principle. In the formulation of the periodic system it is necessary to explain the order in which the electrons assume their various states, i.e. into which orbital the electron falls when we pass from an atom with atomic number to the succeeding atom with atomic number Z Each electron... 

When n = 1, / — o and m = o, s may have the values 1/2 it therefore follows that the first orbital, i.e. when n = 1, can accommodate no more than two electrons. If a third electron was introduced into this orbital, it would also have the values = 1, / = o, m = o and either s = + 1/2 or — 1/2 and thus would correspond exactly to the state of one of the electrons already contained within the orbital, its entry is thus prohibited by the Pauli principle. These deductions are in direct agreement with the periodic classification of the elements in which the first two elements, viz hydrogen... 

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