Periodicity of properties

Quantum mechanics has shown that periodicity is conditioned by the repetition of the configurations of outer electrons and it is natural that only those properties which are concerned with the structure of the outer electrons of the atoms should reveal periodicity. Thus it is found that ionization potentials, ionic dimensions, polarisation etc when considered as a function of atomic number give a curve similar to the atomic volume curve. Other 

A study of properties which sho w p eric dicity is therefore most important, 

Consider 1 the series of elements in the first and second groups shown in  

The energy involved in liberating an electron from an atom of an alkaline earth metal is greater than that required in the case of the corresponding alkali metal thus we may conclude that an unpaired s electron is removed from an atom much more easily than a paired one. This indicates that the pairing of two electrons in an s orbital increases the attraction energy between an s electron and the atom. 

The inner shells of gallium and zinc are identical, whereas those of gallium and calcium are not (see below). 

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Why was Mendeleev so confident that the elements he predicted actually existed This is not a question about his confidence in their periodic law (that, as he formulated it, the elements, if arranged according to their atomic weights, exhibit an evident periodicity of properties (Mendeleev [1889], p. 635)), but rather about an implicit conceptual move. Granted that the gaps in Mendeleev s table represented genuine possibilities, elements that could exist, why assume that the possibilities would [be] v realized (9). 

Complied a periodic table of 56 elements based on the periodicity of properties such as molar volume when arranged in order of atomic weight. Meyer and Mendeleev produced their periodic tables simultaneously. 

Part II Derivation of thermochemical data with respect to the periodicity of properties and their interrelations... 

After the last electron goes into neon (Z — 10), there are no more possible combinations of quantum numbers having n = 2. The outermost electron of sodium must go into a higher energy state with n = 3, much farther from the nucleus. Thus, the outermost electron of sodium, like that of lithium, may be easily lost. More generally, since the chemical properties of elements are determined by their outermost (valence) electrons, the periodicity of properties naturally arises from the quantum restrictions. 

The periodicity of properties of the elements with increasing atomic number may be effectively shown by arranging the elements in a table, called the periodic table or periodic system of the elements. Many alternative forms of the periodic system have been proposed and used. We shall base the discussion of the elements and their properties in this book on the simple system shown as Table 5-1 (it is also reproduced inside the front cover of the book). 

FIG. 5-1. Curve of gram-atomic volume (the volume containing 1 gram-atom) of the elements as function of atomic number, illustrating periodicity of properties. 

There is a periodicity of properties of elements, and these properties are related to numbers of electrons and their energy states in elemental atoms. A classification of elements is possible, based on similarities and differences. Biological substitution of one element for another is thus possible when the preferred element is scarce, as explained in Sections 3.1 and 3.2. 

There is a periodicity of properties of elanents, and these properties are related to numbers of electrons and their energy states in elanental atoms. 

The elements, if arranged according to their own atomic weights, present a periodicity of properties. 

Periodicity of properties means that, after a certain number of elements, an element of similar properties to an earlier one occurs. 

The periodicity of properties of the elements, as functions of the atomic number, is illustrated by the observed values of the interatomic distances in the metals, as shown in Figure 17-2. These values are half of the... 

Part II Derivation of Thermochemical Data with Respect to the Periodicity of Properties and Their Interrelations... 

A]ll masses are nothing but aggregations, or additions, of chemical atoms which would best be described as chemical individuals.. .. The periodic law has shown that our chemical individuals display a harmonic periodicity of properties, dependent on their masses. [Mendeleev,... 

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