There are more than a hundred chemical elements in the world. A Periodic Table is an arrangement of those elements, according to their scientific properties.
|Standard form of the periodic table (Courtesy: Wikipedia)|
Scientists had begun efforts to arrange the known elements in some order years ago, since many elements showed some kind of relations among them. The great scientist who first designed something resembles the modern periodic table was the Russian chemist Dmitri Mendeleev.
Mendeleev began to think about the indiscipline in chemistry during the writing of his book titled Basic Principles of Chemistry which was eventually published in 1870. There were already a lot of elements known to the scientific world then and some of the scientists had attempted to classify and arrange them. They included Johann Dobereiner, Antoine Lavoisier, John Newlands and Lothar Meyer.
Mendeleev came across the studies of Dobereiner and Newlands. They had concluded in their research that the properties of elements were closely related to their atomic weights. Taking this as a reference Mendeleev arranged the 63 known elements in the ascending order of atomic weight, classified into 7 groups. The table was published in 1869. He revised it two years later.
Mendeleev received flak from many scientists in the initial days for discrepancies in the table. One of the reasons for the criticism was that he had assigned some elements in places not corresponding to their atomic weights. He had also left some spaces blank. He argued that they were for the elements yet to be discovered. He even went as far as to predict the properties of some of them.
However, not much later, much of his predictions were proved to be right. In the following 20 years the elements belonging to the blank squares of the periodic table were discovered and their properties were not very different from what he had predicted. The noble gases discovered by William Ramsay also found a place in the table as a special column.
The discovery of atomic structure and atomic particles further discrepancies in Mendeleev’s table. Henry Mosley later discovered that rather than Atomic Mass, Atomic Numbers were the basis of the properties of elements. He rearranged Mendeleev’s table. A major change since then was brought by Glenn Seaborg when he proposed the induction of the newly discovered super heavy elements. Known as Lanthanides and Actinides, these elements found place in the table, creating the modern Periodic Table. According to the discovery of new elements, it is still undergoing changes.