Mendeleeff periodic table

For a long time tellurium was a puzzle to chemists because its atomic weight exceeded that of iodine, which was contrary to what was to be expected from MendeleefFs periodic table. Believing in the absolute truth of MendeleefFs system, many chemists made a study of the atomic weight of tellurium and probably methods of purification of no element have ever been so carefully studied as those of tellurium. The classical research of Baker and Bennett in 1907 appeared to confirm for all time that tellurium must be regarded as an exception to the Periodic Law. As a mean of 43 determinations obtained from various highly purified derivatives of the element a mean value of 127 605 (O = 16 000) was found — a value that is accepted to-day (1950) by the Committee on Atomic Weights of the International Union of Chemistry, in the form of 127 61. 

Very soon afterwards, however, two scientists independently produced the definitive statement on the classification of the elements - Julius Lothar Meyer (1830-95) in Germany and Dmitri Ivanovich Mendeleev (1834-1907) (also spelled Mendeleeff or Mendelejeff) in Russia. It is the latter who is now credited with the construction of the first periodic table. At the age of 35, Mendeleev was Professor of Chemistry at the University of St Petersberg, when he published his first paper (1869) on the periodic system. He was apparently unaware of the work of Newlands or Lothar Meyer, but came to the same conclusions, and was also prepared to go further, and predict that certain elements must remain to be discovered because of discrepancies in his table. Amongst other things, he concluded the following ... 

A remarkable property of the atomic weights was discovered, in the sixties, independently by Lothar Meyer and Mendeleeff. They found that the elements could be arranged in rows in the order of their atomic weights so that similar elements would be found in the same columns. A modernised form of the Periodic Table will be found on pp. 106, 107. It will be noticed, for example, that the "alkali" metals, Lithium, Sodium, Rubidium and Caesium, which... 

W. Werner drew attention to the fact that the elements which show a tendency to form oxyfluorides occupy neighbouring positions in the periodic table of D. I. Mendeleeff, viz. 

MANY SCIENTISTS HAD NOTICED THAT IF YOU LINE UP THE ELEMENTS ACCORDING TO ATOMIC WEIGHTS, CERTAIN CHEMICAL TRAITS OCCUR PERIODICALLY. THE RUSSIAN SCIENTIST, DMITRI MENDELEEFF, ON THIS BASIS DISCOVERED THE PERIODIC LAW AND DEVELOPED THE PERIODIC TABLE. 

In general, for a particular value of the principal quantum number, there cannot be more than two s, six />, ten d and fourteen/ electrons and the total possible number of electrons for a given value of n is therefore equal to 2n. Thus the introduction of the concept of spin leads to the doubling of the number of possible electronic states (equation 1.39). The possible distribution of electrons for a hydrogen like atom is shown in Table V and it is seen that the series 2, 8, 18, 32,. . . which has arisen from the application of the Pauli principle is in agreement with the numbers of elements occurring in the periodic table of Mendeleeff. The electron shells with values for the principal quantum number i, 2, 3, 4, etc are often referred to as the /if, L, Af, JV, etc shells. 

The Periodic Table. Numerous attempts had been made to classify the elements in such a way that those with similar chemical properties are grouped together in order of increasing atomic weight, but it was not until 1869 that success w as achieved by Mendeleeff. 

In August 1869 Mendeleeff presented to the Second Congress of Russian Naturalists in Moscow a communication on The Atomic Volumes of the Simple Bodies this was printed in the Transactions (pp. 62-71) and contains a periodic table in the modern form, as far as the elements whose atomic weights were well established is conceriied, and also the triads of transitional elements. In this table the groups are not separated, e.g. group I contains Li, Na, K, Cu, Rb, Ag, Cs, and group II Be, Mg, Ca, Zn, Sr, Cd, Ba. 

In 1871 Mendeleeff published a long paper in which the periodic table is improved in one or two places (e.g. indium is put into group III instead of II — Lothar Meyer had suggested this) and assumes more or less its modern... 

Inorganic Syntheses (McQraw-Hill, 1939-1960) is a compilation in six volumes of methods for the synthesis of inorganic compounds, each of which has been carefully checked and tried in the laboratory. Chapters are arranged according to Mendeleeff s periodic table. Many syntheses are preceded by a critical survey of known methods. A detailed description is given of laboratory procedure, with an account of the properties of the substance and a reference to the literature. A list of cross references at the head of each chapter indicates where related syntheses are found in other chapters. There is a cumulative index as well as a detailed table of contents which lists compounds synthesized. 

TABLE XII. —PERIODIC ARRANGEMENT OF THE ELEMENTS, ACCORDING TO MENDELEEFF. 

When n = 2, / can have the values o and 1 and hence both s and p orbitals are permissible. If / = o, then m = o and this orbital may contain two electrons having the values of s -h 1/2 and — 1/2. When / = 1, three values of m are permissible, viz + i5 o, — 1 and to each of these orbitals there may be ascribed the values s = 1/2. Thus when the principal quantum number has the value 2, there exist one s and three p orbitals which may contain 2 and 6 electrons respectively, i.e. eight in all. These four orbitals permit the construction of the second period of the MendeleefF table containing eight elements. 

B. N. Menschutkin says Mendeleeff s first table was printed in the middle of February 1869 and sent to several chemists. He had appreciated the periodic relation at the end of 1868. An essay was prepared for reading to the Russian Chemical Society (founded on 26 October 1868) and was read on 6 March 1869 by N. A. Menschutkin, Mendeleeff being ill. The publication in April contains the table printed in February, and also the first statement of the periodic law, and the deductions from it that a) the atomic weights of some elements must be altered to fit into the table, b) undiscovered elements must exist, filling vacant places in the table. The paper contains the eight statements ... 

Lothar Meyer s first publication on the periodic law, dated in December 1869, appeared in 1870. It refers to the German abstract (1869) of Mendeleeff s paper and gives a table, said to be essentially identical with that given by Mendeleeff , no claim for originality being made. 

An account of the periodic law was given in 1876 by H. E. Armstrong and from about 1884 appeared in several English text-books. Thomas Carnelley extended the periodicity of physical properties to compounds. Wyrouboff, who did important research on isomorphism, said Mendeleeff s selection of the typical oxides (see top of table on p. 896) is arbitrary sometimes the lower oxide is selected (CugO), sometimes the higher (Mn207). 

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