Atomic structure and Mendeleev’s Periodic System of chemical elements


The Ministry of Education and Science of the Russian Federation Kazan National Research Technological University







E. Starodubets, A. Kuznetsov



ATOMIC STRUCTURE AND MENDELEEV’S PERIODIC SYSTEM OF CHEMICAL ELEMENTS


Tutorial

















Kazan
KNRTU Press
2019

       UDC 54;546(075)




Published by the decision of the Editorial Review Board of the Kazan National Research Technological University

Reviewers:
Ph. D. N. Ulakhovich Ph. D. S. Podyachev


       Starodubets Е.
       Atomic structure and Mendeleev’s Periodic System of chemical elements : tutorial / Е. Starodubets, A. Kuznetsov; The Ministry of Science and Higher Education of the Russian Federation, Kazan National Research Technological University. - Kazan : KNRTU Press, 2019. - 88 p.

       ISBN 978-5-7882-2750-4

     The tutorial is dedicated to the 150th anniversary of the Mendeleev Periodic Table and the International Year of the Periodic Table of chemical elements. The study guide contains the facts from the history of the Periodic Table discovery, the modern information about the structure of the atom and periodic properties of chemical elements and their relation with the Periodic Law.
     The tutorial is intended for the students learning in the educational program in the area “Chemical Technology”, who study the discipline “General and Inorganic Chemistry”, as well as for students from foreign countries to study in the framework of international educational programs, and for graduate students and teachers of chemistry.
     The tutorial was prepared by Department of Inorganic Chemistry.

UDC 54;546(075)

ISBN 978-5-7882-2750-4    © Starodubets Е., Kuznetsov A., 2019
                          © Kazan National Research Technological
University, 2019

                PREFACE





In 1869, the Russian chemist Dmitri Mendeleev and the German chemist J. Lothar Meyer, working independently, made similar discoveries. They found that when they arranged the elements in order of atomic mass, they could place them in horizontal rows, one row under the other, so that the elements in each vertical column have similar properties. A tabular arrangement of elements in rows and columns, highlighting the regular repetition of properties of the elements, is called a periodic table.
      Eventually, more accurate determinations of atomic masses revealed discrepancies in the ordering of the elements. However, in the early part of the last century, it was shown that the elements are characterized by their atomic number, rather than atomic masses. When the elements in the periodic table are ordered by atomic number, such discrepancies vanish.
      In the modern version of Mendeleev’s Periodic Table with the elements arranged by their atomic number each cell contains the atomic symbol of an element, its atomic number and mass. This is a convenient way to present brief information about chemical elements, which we will use when studying the Periodic Table. As we study the subject matter of chemistry, we will see how useful the Periodic Table is.
      The Periodic Table of chemical elements is one of the most important scientific achievements, reflecting the essence of not only chemistry, but also physics. It is a unique tool that gives scientists the ability of predicting the origin and properties of elements on Earth and throughout the Universe. In 2019, it is celebrated the 150th anniversary of the creation of the Periodic Table by the Russian scientist Dmitri Ivanovich Mendeleev. This year is proclaimed by the UN General Assembly and approved by the General Conference of UNESCO as the International Year of the Periodic Table of chemical elements. Therefore, we dedicated our study guide to this momentous event.
Elena E. Starodubets and Andrey M. Kuznetsov

October 2019


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                HISTORY OF THE PERIODIC TABLE


                The development of experimental chemistry, the discovery of a large number of new chemical elements and the study of their chemical and physical properties by the 18th century set before scientists the problem of classifying elements.




       Early attempts to classify known chemical elements were made in an era when there were no clear ideas about the structure of atoms. In the late XVIII - early XIX centuries, chemists tried to create classifications of chemical elements according to their physical and chemical properties, in particular on the basis of the state of aggregation of the element, specific gravity (density), electrical conductivity, basicity-acidity, etc.
       In 1789, Antoine Lavoisier published a list of 33 chemical elements, grouping them into gases, metals, nonmetals, and earths. Chemists spent the following century searching for a more precise classification scheme.
       In 1793, the German chemist J.B. Richter published the book “Stoichiometry or the Art of Measuring the Chemical Elements”, where he arranged metals with similar properties (sodium and potassium; magnesium, calcium, strontium and barium) in order of increasing atomic mass.
       In 1829, Johann Wolfgang Dobereiner observed that many of the elements could be grouped into triads based on their chemical properties. Lithium, sodium, and potassium, for example, were grouped together in a triad as soft, reactive metals.

1 Li Na K 
2 S  Se Te
3 Cl Br I 
4 Ca Sr Ba

Dobereiner Triads (1817)

      Dobereiner also observed that, when arranged by atomic weight, the second member of each triad was roughly the average of the first and the third. This became known as the Law of Triads: "Chemically analogous elements arranged in increasing order of their atomic weights formed well marked groups of three called Triads in which the atomic weight of the middle element was found to be generally the arithmetic mean of the atomic weight of the other two elements in the triad”.


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      German chemist Leopold Gmelin worked with this system, and by 1843 he had identified ten triads, three groups of four, and one group of five. Jean-Baptiste Dumas published work in 1857 describing relationships between various groups of metals. Although various chemists were able to identify relationships between small groups of elements, they had yet to build one scheme that encompassed them all.
      In 1857, German chemist August Kekule observed that carbon often has four other atoms bonded to it. Methane, for example, has one carbon atom and four hydrogen atoms. This concept eventually became known as valence, where different elements bond with different numbers of atoms.
      In 1862, Alexandre-Emile Beguyer de Chancourtois, a French geologist, published an early form of periodic table, which he called the telluric helix or screw. He was the first person to notice the periodicity of the elements. With the elements arranged in a spiral on a cylinder by order of increasing atomic weight, de Chancourtois showed that elements with similar properties seemed to occur at regular intervals. His chart included some ions and compounds in addition to elements. His paper also used geological rather than chemical terms and did not include a diagram. As a result, it received little attention until the work of Dmitri Mendeleev.
      In 1864, Julius Lothar Meyer, a German chemist, published a table with 28 elements. Realizing that an arrangement according to atomic weight did not exactly fit the observed periodicity in chemical properties he gave valency priority over minor differences in atomic weight. A missing element between Si and Sn was predicted with atomic weight 73 and valency 4.

            4 werthig   3 werthig   2 werthig 1 werthig 1 werthig   2 werthig
                -            -          -         -       Li=7,03   (Be=9,3?)
Differenz=      -            -          -         -        16,02     (14,7)  
              C=12,0    N=14,04      0-16,00   Fl=19,0  Na=23,05    Mg=24,0  
Differenz=     16,5        16,96      16,07     16,46      16,08      16,0   
             Si=28,5      P=31,0     S=32,07  Cl=35,46  K=39,13      Ca=40,0 
Differenz= 89,1/2=44,55    44,0       46,7      44,51      46,3       47,6   
                -         As=75,0    Se=78,8  Br=79,97    Rb=85,4    Sr=87,6 
Differenz= 89,1/2=44,55    45,6       49,5      46,8       47,6       49,5   
             Sn=117,6   Sb=120,6    Te=128,3   J=126,8  Cs=133,0    Ba=137,1 
Differenz= 89,4=2*44,7  87,4=2*43,7     -         -     (71=2*35,5)     -    
             Pb=207,0   Bi=208,0        -         -     (Tl=204?)       -    

 Julius Lothar Meyer's periodic table, published in "Die modernen Theorien der Chemie" (1864)

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       Concurrently, English chemist William Odling published an arrangement of 57 elements, ordered on the basis of their atomic weights. With some irregularities and gaps, he noticed what appeared to be a periodicity of atomic weights among the elements and that this accorded with "their usually received groupings". Odling alluded to the idea of a periodic law but did not pursue it. He subsequently proposed (in 1870) a valence-based classification of the elements.
       English chemist John Newlands produced a series of papers from 1863 to 1866 noting that when the elements were listed in order of increasing atomic weight, similar physical and chemical properties recurred at intervals of eight. He likened such periodicity to the octaves of music. Newlands arranged all the known elements in the form of a table. There are some vertical rows, later termed as periods, and vertical columns which were later termed as groups. Newland's periodic table is shown below:

H      Li  Be     В    c  N      0     
  F    Na  Mg     Al   Si   P    S     
Cl     К   Ca     Cr   Ti   Mn   Fe    
Co, Ni Cu  Zn     Y    In As     Se    
Br     Rb Sr    Ce, La Zr Di, Mo Ro, Ru
Pd     Ag  Cd     U    Sn   Sb     1   
Те     Cs Ba, V   Ta   W    Nb   Au    
Pt, Ir Os  Hg     Tl   Pb Bi       Th  

Newlands’ Octaves

      This so termed Law of Octaves was ridiculed by Newlands' contemporaries, and the Chemical Society refused to publish his work. Nonetheless, Newlands was able to draft a table of the elements and used it to predict the existence of missing elements, such as germanium.
      The Russian chemist G.I. Gess, in the textbook “Foundations of Pure Chemistry”, published in 1849, distributed the nonmetals elements known at that time into four groups according to the proximity of their chemical properties: carbon - boron - silicon; nitrogen - phosphorus - arsenic; sulfur -selenium - tellurium and chlorine - bromine - iodine. It is believed that it was Hess who introduced the concept of "group of elements" and the groups defined by him were included in the D.I. Mendeleev periodic table almost unchanged.


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Mendeleev and the Periodic Table


The periodic table was originally based on experimental observations of the chemical and physical properties of the elements. The Russian chemist Dmitri Ivanovich Mendeleev, who was professor of chemistry at the University of St. Petersburg, was the most important contributor to the early development of the periodic table. Mendeleev could not find a textbook that suited him and decided to write his own. In the course of writing his book, Mendeleev examined relationships between the properties of the elements and their compounds trying to find a system of organization that would help his students to learn chemistry. He discovered the periodic law, which he published in 1869, and constructed a periodic table soon afterward.
       According to Mendeleev’s periodic law, “the properties of the elements are a periodic function of their atomic weights”. Mendeleev realized that, when placed according to their atomic weights (masses), several elements were out of place. He concluded that the atomic weights must be               -
wrong and put the elements where they belonged on basis of their properties. Table 1 shows Mendeleev’s Periodic Table of 1871.
Because a number of elements had not yet           Dmitri Ivanovich
discovered, there were several blank spaces           Mendeleev
(for example, at 44,       68 and 72) in              (1834-1907)
Mendeleev’s Table.
       Like Newlands and Meyer, Mendeleev in his Table arranged the elements in ascending order of their atomic mass. However, unlike Newlands, Mendeleev, based on the properties of the elements and taking into account the forms of the compounds formed by them, left empty places in the table for still unknown elements (eka-silicium, eka-boron, eca-aluminum) and placed elements with similar properties into different groups without trying to put them in the same cell. Besides, in several cases, the elements were arranged in accord with their properties despite the discrepancies in the atomic mass: for example, Co (58.9332) and Te (127.60) with a larger atomic mass were placed earlier than those with a smaller atomic mass Ni (58.7) and I (126.9045). On basis of the properties of neighboring elements, Mendeleev predicted the properties of these unknown elements. Three of these missing elements were discovered


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within the next 15 years. The fact that the properties of the newly discovered elements were very similar to the properties predicted by Mendeleev (see Table 2) provided convincing evidence for both the correctness and the usefulness of the periodic table. The last missing element to be found was francium, which was not discovered until 1939.


Table 1. Mendeleev’s Periodic Table in His Paper Published in the German Journal Annalen der Chemie und Pharmacie in 1872

Reihen                                   Gruppe IV. Gruppe V. Gruppe VI. Gruppe VII.                   
       Gruppe 1.  Gruppe II. Gruppe III.    RH4     RH3       RH2            RH      Gruppe VIII.      
       R2O            RO     R2O3           RO2       R2O5    RO3           R2O7            RO4        
1      H = 1                                                                                           
2      Li =7      Be = 9,4   В = 11      C = 12     N = 14    О = 16     F = 19                        
3      Na = 23    Mg = 24    Al = 27,3       Si =28     P =31     S = 32   Cl = 35,5                   
4      К =39      Ca =40     --- =44     Ti =48     V = 51    Cr = 52    Mn = 55     Fe = 56. Co = 59, 
5      (Cu = 63)  Zn = 65    - =68       - =72      As = 75   Se = 78    Br = 80       Ni = 59, Cu =63.
6      Rb = 85    Sr = 87    ?Yt = 88    Zr =90     Nb =94    Mo = 96    --- =100    Ru = 104, Rh =104.
7      (Ag = 108) Cd = 112   In = 113    Sn = 118   Sb = 122    Те = 125 J = 127     Pd = 106, Ag = 108
8      Cs = 133   Ba = 137   ?Di = 138   ?Ce = 140  -         -          -           _ _ _ _           
9      (-)        ---        ---                ---       ---        ---         ---                   
10     -          ---        ?Er = 178   ?La =180   Ta = 182  W = 184    -           Os = 195, li =197,
11     (Au =199)  Hg = 200   T1 = 204    Pb = 207   Bi = 208                         Pt = 198, Au = 199
12                                       Th =231              U = 240                                  

Table 2. Some Properties of Germanium

       Property        Predicted by Mendeleev   Found by Winkler in  
                              in 1871                  1886          
Atomic mass                      72                                  
Density, g/cm3                  5.5                    72.32         
Molar volume, sm3/mol           13.1                   5.47          
Color                        Diny gray                 13.22         
Heating in air gives            EO2                Grayish white     
Properties of EO2       High melting point;            GeO2          
Properties of chloride  Density = 4.7 g/cm3   Melting point, 1086 oC;
                           Formula, ECh;       Density = 4.703 g/cm3 
                       Boiling point a little     Formula, GeCh;     
                           under 100 oC;       Boiling point, 86 oC; 
                        Density « 1.9 g/cm3    Density « 1.887 g/cm3 

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      A number of changes have been made in the periodic table since 1871. When the noble gases helium and argon were isolated from air in 1894, another column was added. The existence of neon, krypton, xenon, and radon was then predicted from the periodic law, and these gases were soon discovered. The position of the lanthanides, an early problem, was worked out by Bohr in 1913. American chemist Glenn Seaborg realized in 1944 that the elements beginning with actinium (atomic number 89) form a second f-block series like the lanthanides. Chemists had previously thought that these elements were transition elements. The ability to predict the properties of the transuranium elements (the elements with atomic number greater than 92) was of great help in working with these elements when they were synthesized. All transuranium elements are radioactive, and some have only been made in minute amounts (a few atoms).
      The problem of the elements that were out of order according to their masses (Ar and K, Co and Ni, Te and I, and Th and Pa) was solved in 1913 when Moseley discovered atomic numbers. According to the modern periodic law, the properties of the elements are a periodic function of their atomic numbers, not of their atomic masses. The atomic number of an element describes the number of electrons outside the nucleus, The arrangement of the electrons in shells and subshells, the electron configuration of the elements, determines the properties of the elements. Why did atomic mass work so well as a basis for organizing the properties of the elements? The answer to this question lies in the “aufbau” process - as proton are added to the nucleus, the mass of the atom increases. As protons are added to the nucleus, neutrons must also be added, and mass increases faster than atomic number. However, the order according to atomic number is about the same as the order according to atomic mass. A few elements are out of order when arranged according to atomic mass because naturally occurring samples of these elements contain unusually high proportions of heavy isotopes.
      Mendeleev, a very practical man, used his scientific knowledge to improve the yields and quality of Russian crops and contributed to the development of the chemical and petroleum industries. However, his forward-looking political views were not popular with the czar. In 1890 he carried a request for the relief of unjust conditions from the students at the university to the administration and was retired early.
      Mendeleev’s periodic table was published in a German journal in 1872. In German, “Reien” means row, “Gruppe” means group, and “J” is the symbol for iodine. In the formulas for oxides and hydrides, the letter

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“R” is used to represent any of the elements in a group. Notice that the numbers that are now subscripts in formulas were superscripts in Mendeleev’s day. The numbers after the equal signs in the body of the table are the atomic masses of the elements; the elements are arranged in order of increasing atomic mass. Mendeleev placed elements with similar properties in the same group, leaving spaces for elements that were unknown, such as the elements with atomic masses 44, 68, and 72.
       Periodic table has stood the test of time. In 1875, a French chemist Paul-Emile Lecoq de Boisbaudran discovered gallium (eka-aluminium). Boisbaudran said he named it after the Latin word “France”. In 1879, a Swedish chemist Lars Nielsen discovered scandium (eka-boron). He named it scandium because he discovered it in rocks from Scandinavia. In 1886, a German chemist Clemens Winkler found the new element along with silver and sulfur, in a rare mineral called argyrodite. Winkler named it germanium (eka-silicium) after his country, Germany.
       A little later, an English scientist, Lord Rayleigh, suspected that nitrogen separated from air by distillation was not really pure. In 1894, Rayleigh and a Scottish chemist William Ramsay separated another inreactive gas from nitrogen. The called the new element argon, after the Greek word for “inactive’. The year 1898 was a good year for Ramsay. It turned out that his sample of argon was impure and contained three other gases. Working with his assistant Morris Travers, he discovered neon in May, krypton in June, and xenon in July. They had found three new elements in just six weeks! All the elements discovered were placed in a separate zero group of the periodic table. A German chemist, Friedrich Dorn, discovered a sixth inreactive gas called radon in 1900. But Ramsay was the first person to separate it, ten years later.
       By now, Mendeleev’s periodic table has been significantly expanded - since its inception, more than 50 elements have been discovered (Table 3). The prophetic words of Mendeleev, spoken by him in 1905, are confirmed: "Apparently, the future does not threaten the periodic law with destruction, but promises only superstructures and development."
       By 2019, declared by the United Nations as the International Year of the Periodic Table of Chemical Elements, mankind has 118 elements that make up seven full periods. In recent decades, scientists from different countries of the world combine their knowledge and experience in searching for new elements; therefore, the “superstructure” of the periodic table will be continued.

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