Periodic Table Turns 150

The ‘Periodic Table of Elements’ or ‘The Table’ has turned 150 years old in 2019. The United Nations General Assembly and UNESCO have decided to observe 2019 as the “International Year of the Periodic Table of Chemical Elements (IYPT2019)”.

History of the Periodic Table

• Antoine-Laurent de Lavoisier wrote the Traité Élémentaire de Chimie (Elementary Treatise of Chemistry) in 1789. He also defined an element that can’t be broken down into simpler substances. He classified them in terms of their properties.
• Johann Wolfgang Döbereiner in 1829 found that he could form some of the elements into groups of three similar property possessing elements. He termed these groups as triads.
• Alexandre-Emile Béguyer de Chancourtois noticed periodicity in elements for the first time which means similar elements will occur at regular intervals when arranged in order of their atomic weights. In 1862 he devised Vis tellurique (the ‘telluric helix’), which was a form of a periodic table.
• John Newlands in 1864, classified the then 62 known elements into eight groups according to their physical properties. He was the first to assign atomic numbers.
• Dmitri Mendeleev arranged the elements by atomic mass, corresponding to relative molar mass. The modern Periodic Table was written by him on 17^th February 1869. He had also predicted the discovery of many other elements in the future. He had put 63 elements in his table that were known during that time.
• Today the Table has 118 elements.
• Mendeleev had said the properties of elements depended upon the atomic weights. It was in 1913, when Moseley proved that the pproperties of the elements depend upon the periodic functions of their atomic numbers.

Who is Dmitri Mendeleev?

Dmitri Ivanovich Mendeleev was a Russian chemist and inventor who was born in the Verkhnie Aremzyani village, near Tobolsk in Siberia, to Ivan Pavlovich Mendeleev and Maria Dmitrievna Mendeleeva. He formulated the Periodic Law that is now the basis for the modern Periodic table

Comment

Mendeleev’s table laid the basic foundation for the feature that ‘properties of elements are periodic functions of the inherent properties of its atoms’. Scientists remember him fondly because his discovery is the basis for solving the puzzles of nature. He has never won a Nobel Prize till now, however, element 101 is rightfully named as Mendelevium (Md).