Periodic table of elements

Periodic Table of Chemical Elements . The Periodic Table of Chemical Elements classifies, organizes and distributes the different chemical elements, according to their properties and characteristics. It is attributed to the Russian chemist Dimitri Ivanovich Mendeleyev , who ordered the elements based on the manual variation of the chemical properties, although Julius Lothar Meyer , working separately, carried out an ordering based on the physical properties of the atoms . The current form is a modified version of Mendeleyev’s, it was designed by Alfred Werner .

Summary

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• 1 History
  • 1 Chemical Element
  • 2 First Tables
  • 3 atomism Dalton
  • 4 Classifications of Chemical Elements
    • 4.1 Lavoisier classification
    • 4.2 Döbereiner Triads
    • 4.3 Chancourtois propellers
    • 4.4 Newlands Eighths Law
    • 4.5 Mendeleev’s Periodic Table
  • 2 Table of Chemical Elements
  • 3 Table types
    • 1 Short table
    • 2 Long table
    • 3 Extended long table
  • 4 New alternative versions to the traditional one
  • 5 Updates to the Periodic Table
  • 6 Sources

History

Dimitri Ivanovich Mendeleyev

Some chemical elements have been known since ancient times, alchemists being the fundamental architects of this chemical knowledge before this science was defined as such. The gold (Au), the silver (Ag), the lead (Pb) and other elements such as mercury (Hg), the sulfur (S), the arsenic (As), tin (Sn) and others since ancient times, until more current discoveries like phosphorus (P) in 1669 . This allowed Antoine Lavoisier to write a list of 33-element simple substances, but in 1830 This list was expanded to 55 simple elements which was expanded with the invention of the spectroscope.

The study of common properties and their classification, the emergence of the notion of atomic mass were forming the low foundations which made it possible to discover the periodicity of chemical elements based on their atomic number and chemical properties based on a sufficient number of individual elements of it.

Chemical element

The very concept of element in its modern notion was consolidated throughout the 17th century , where element a

“certain primitive and simple bodies that are not made up of other bodies, nor of each other, …”

First Tables

Already in the eighteenth century the affinity tables appear, in an attempt to understand the chemical composition and order the elements. It also allowed us to differentiate at that time which substances were chemical elements, and which were not, as well as their properties and how to obtain them.

Dalton’s Atomism

At the beginning of the 19th century , the development of a new conception of atomism began thanks to the work of John Dalton . they were integrated to the definition of elements given by Lavoisier and other empirically obtained laws at that time. Within them, the laws of proportions were used by Dalton to assume how atoms were combined establishing the mass of a hydrogen atom (H) as the reference unit (in addition to using the mass of a hydrogen atom as reference, other ). and from the same calculation the rest of the masses or atomic weights, by means of this he could build a system of relative atomic masses.

Chemical Element Classifications

Lavoisier classification

Lavoisier himself gave the first classification of elements grouping them into:

1. metals
2. no metals
3. metalloids or transition metals

which was rejected due to the fact that there were many differences between the physical and chemical properties of the grouped elements.

Döbereiner Triads

Another attempt to group chemical elements with similar properties was given by the German chemist Johann Wolfgang Döbereiner , which revealed the similarity that existed between the properties of certain groups of three elements, with a gradual variation from the first to the last, calling to these triated elements, being in 1850 up to 20 of them showing the existence of a certain regularity between the chemical elements.

Chancourtois propellers

Chancourtois propellers

In 1864 , Chancourtois built a paper propeller, on which the known elements were ordered by atomic weights, wound on a vertical cylinder. The corresponding points were found to be about 16 units apart. The similar elements were practically on the same vertical line, indicating a certain periodicity, but their diagram seemed very complicated and received little attention.

Newlands Eighth Law

Series Law of the eighths.

In 1864 the English chemist John A. Reina Newlands created the octave law, realizing that by ordering the elements in increasing order of their atomic weights (ignoring hydrogen), the eighth element from any other had properties very similar to the first from which it was counted.

This regularity allowed the ordering of the elements in families or groups with properties very similar to each other and in periods formed by eight elements whose properties were gradually changing.

Since this rule was no longer followed from calcium, this order was not appreciated by the scientific community.

Mendeleev’s Periodic Table

Table manuscript

In 1869 Mendeleev published his first table of elements in Germany , a year later Julius Lothar Meyes did it .

In this table the elements were placed in increasing order of their atomic masses, as well as elements with common properties such as valence in the same group. Mendeleyev’s first periodic classification was not well received at first. After several modifications, in 1872 he published a new Periodic Table consisting of eight columns divided into two groups each, which over the years were called family A and B. In his new table, he lists the general formulas of hydrides and oxides. of each group and therefore, implicitly, the valences of those elements. This table was completed in the late 19th centurywith one more group, group zero, made up of the noble gases discovered during those years in the air. The Russian chemist did not accept such a discovery in principle, since those elements had no place in his table. But when, due to their chemical inactivity (zero valence), they were assigned group zero, the Periodic Table was more complete.

First table

Mendeleyev’s great merit was to forecast the existence of elements . He left empty boxes to place the elements whose discovery would take place years later. He even predicted the properties of some of them: gallium (Ga), which he called eka-aluminum because it is located under aluminum; the germanium (Ge), to which called Eka-sicilio; the scandium (Sc); and technetium (Tc), which, chemically isolated from remnants of a synchrotron in 1937 , became the first element produced predominantly artificially.

In addition to his table, Mendeleev proposed the periodic law stating that: All elements must be arranged in ascending order based on their atomic mass , however, it presented problems, since some elements did not seem to have a suitable place in the table of agreement to their atomic mass, since their properties were not similar to those of the elements that preceded them or were different from those of the elements of the group that corresponded to them.

Later, when he knew better the atomic structure of the elements, he found greater periodicity in the physical and chemical properties, ordering the elements in an increasing way based on their atomic number. From this classification, Mendeleev’s periodic law was modified, establishing the modern periodic law.

Chemical Element Table

The periodic table or system is the graphic form of the periodic Law , it is the scheme of all the chemical elements arranged in order of increasing atomic number and in a way that reflects the structure of the elements. Its basis is the “Periodic Law”, which establishes that the physical and chemical properties of the elements tend to repeat themselves systematically as the atomic number increases. All the elements of a group have a great similarity and, generally, differ from the elements of the other groups.

Table types

Each author is tempted to draw a table where, according to him, the concepts of chemical periodicity are better handled. The most important tables are commonly known as: Table short , long Table and Table long extended

Short board

Direct derivation of the original proposed 8-column Periodic Table from Mendeleev-Meyer; Modifications were made to it as time and knowledge progressed; the presence of one more vertical group is already noticeable; the noble gases group, unknown to Mendeleev.

Longboard

Very useful modification, which is also often known as Borh’s table. It is constructed in such a way that it reflects Borh’s theory of electronic distribution. In the verticals are the elements whose final electronic distribution is coincident, in essence the long table derives from Mendeleev’s original, extending the long periods (fourth, fifth and sixth) and cutting the short periods in two to accommodate the middle the series of the transition elements. Thus long periods are generated but only from the fourth period.

In this type of table, each period corresponds to the formation of a new electron shell. The aligned elements have strictly analogous electronic structures. The beginning and end of a long period represent the addition of electrons in a valence shell; in the central part the number of electrons in an underlying shell increases.

The long form table was prepared by Alfred Werner. This table is made up of all the elements found in nature, as well as synthetics, and they are arranged according to the electronic structure of their atoms, observing a progressive arrangement of the valence electrons in energy levels (periods). The elements that present similar external electronic configurations are grouped into vertical columns called families or groups. In addition, for ease of representation, two horizontal rows appear outside the table that correspond to elements that should go in the sixth and seventh period, after the third element of the period. Horizontally the chemical elements are grouped into Groups, which range from group IA to VIIIA, each grouping elements with similar properties, they are distributed in 18 columns (this table is also known as the 18-column periodic table). Also vertically they are arranged in periods of seven elements, they go from the first to the seventh element.

Different types of long form tables have been proposed:

• Periodic Table of 18 columns.
• Block separation of elements.

Long extended table

Modern representation, with the drawback that the graphs are made very extensive, it follows when going through increasing atomic number the filling of orbits proposed by Borh; has

• 34 column periodic table,
• Periodic Table of 32 columns, etc.

The first period has two elements, the second and third have eight, the fourth and fifth have 18 elements, the sixth period 32 elements, and the seventh so far is exhausted with 106 elements.

New alternative versions to the traditional one

Alternative versions of the Periodic Table have appeared in recent years. It should be noted that of Professor Dufour of the Ahuntsic College in Montreal, who has developed a three-dimensional periodic system that reveals the fundamental symmetry of the elements. Other alternatives are those of William B. Jensen , from the University of Cincinnati, with a pyramid shape and that of the Russian Agafoshin, in a spiral, which is gaining popularity is the classification system, which has been adopted by the International Union of Pure and Applied Chemistry (IUPAC). This new system lists the groups consecutively from 1 to 18 through the periodic system.

Periodic systems referring to molecules such as Ray Hefferlin of the Southern Adventist University in Collegedale for diatomic molecules and Jerry R. Dias of the University of Missouri in Kansas City for aromatic hydrocarbons have also been proposed. benzene derivatives. The Days classification system is analogous to the Döbereiner triads: the number of carbon and hydrogen atoms of the molecule in the center of a triad is the average of that which characterizes the molecules that flank it, the same vertically as horizontal.

Updates to the Periodic Table

The General Assembly of the International Union of Pure and Applied Physics (IUPAP), meeting in London, approved the names of three new chemical elements: the 110, 111 and 112, which were named darmstadtium (Ds), roentgenium (Rg) and copernicium (Cn), respectively.

Darmstadtium was discovered in 1994 at the Heavy Ion Research Center in Darmstadt, Germany. It was not a conventional discovery of something that exists in nature but was produced in the laboratory by bombarding a lead of 208 with nickel ions 62. Four atoms of this new chemical element were counted. Until 2001 its existence was not officially recognized.

Roentgenium was discovered the same year as darmstadtium and at the same German institute, but scientists at the time had only obtained three atoms and it was not considered sufficient to be recognized. Eight years later three other atoms were discovered and their existence accepted. It is one of those elements that does not exist in nature naturally, scientists create them by means of particle accelerators to merge nuclei of other elements until obtaining new ones and they disintegrate immediately. Therefore, proving that they have been produced is extremely difficult and it takes years to obtain sufficient and convincing evidence.

Copernicium, also synthetic, is extremely radioactive. It was created, in 1996 , at the same institute in Darmastadt, by bombarding -70 zinc core against a 208 lead target in a heavy ion accelerator, but the result was considered controversial for years and was not recognized as a discovery until its confirmation in 2009 .

The International Union of Pure and Applied Chemistry officially approved the 31 of maypole of 2012 the names of elements 114 and 116, flerovium (Fl) and livermorium (Lv) respectively.

In mid- 2011 , physicists belonging to the Central Institute for Nuclear Research (JINR) in Dubna and the Lawrence Livermore National Laboratory in California officially accredited the synthesization of the two elements. Element 114 was synthesized in December 1998, bombarding the nucleus of plutonium with calcium nucleus , which has 94 and 20 protons respectively. Element 116 was synthesized in July 2000 after bombarding the curium nucleus , which has 96 protons, with a calcium nucleus.