The Periodic Table

What the periodic table tells us? Why its discovery had taken up more than 50 years? Why is Mendeleev considered to be the ‘father’ of the Periodic Table? The periodic table is one of the most noticeable icons in chemistry. This table shows the organization of the elements in horizontal rows, called periods, and in vertical columns, called groups. It is an arrangement according to the increase of their atomic number in each element, which is equal with the number of the protons in the nucleus, and also based on similar chemical behavior and physical characteristics. Although more than 80 scientists tried to organize the elements systematically, the Russian professor of chemistry, Dmitri Ivanovich Mendeleev was the first person who successfully

Many scientists tried to organize the elements in different ways according to their valence, periodicity or whether they are metal, non-metal, gases or earths. One of the earliest attempts to classify the elements were in 1817 when Johann Wolfgang Döbereiner formed some of the known elements into groups of three (he called them ‘triads’) and showed that the properties of the middle element were the average from the properties of the other two elements in each group. Unfortunately, there was a small number of elements that were discovered since that time, so he was unable to organize a few elements and to leave a space for more than 80 undiscovered elements. Several other attempts were made over the next few years to put in order the elements. In 1829 Alexandre-Emile Béguyer de Chancourtois organized the elements according to the increase of their atomic weight and arranged them in a spiral on a cylinder. Despite the arrangement of all known elements he could not have displayed them correctly because of the wrong calculations. Nevertheless, that was the earliest form of the periodic table (Figure 1). The first

He put in order the elements while he was trying to write a textbook in Russian, based on the latest knowledge. He decided to write the textbook in two volumes. When he had completed Volume 1, he realized that he discussed only nine elements in that volume. At that time, the known elements were 63, which mean he had to discuss 54 elements in Volume 2. Mendeleev tried to find the correct way to talk about every element. He stared to write the properties of each element on pieces of cards. When he finished writing their properties he realized that if he put the elements according to the increase of their atomic weight he can group all elements in a small table where everything is explained with few signs. He successfully arranged the elements in a table and published it on 17th of February 1869 titled ‘An Attempt at a System of Elements, Based on Their Atomic Weight and Chemical Affinity’ (Baldwich, Clough, Greenbowe, 2008). The genius of Mendeleev’s table was that he predicted the existence of three previously unknown elements and their properties and had left gaps between the elements in his table. A few years after the discovery of the periodic table there were found all three elements, Mendeleev predicted (NNDB 2014). Despite the discovery of the periodic table, Mendeleev had not predicted the existence