The Periodic table is considered to be the most important classification in chemistry. Mendeleev, a Russian Scientist, was the first to construct a Periodic Table in 1869. He arranged the elements in order of their relative atomic mass. He pointed out that the elements with similar properties kept occurring at regular intervals or periods.
The Mendeleev’s Periodic table had many gaps. He predicted that there were undiscovered elements which could fill these gaps. He even predicted the possible properties of these elements. Later, elements like scandium, gallium, germanium etc. were discovered which fit into the Periodic Table and have the properties as predicted by Mendeleev. This clearly showed the great usefulness of the Periodic Table as it helps us to correlate the properties of elements.
With the discovery of the electronic structure of atom, it became clear that elements do vary regularly, not with their relative atomic mass, but with their atomic number.
THE PERIODIC TABLE
The word “Periodic” means for something to have repeated cycles or something occurring at regular intervals. The Periodic Table shows the arrangement of elements into groups and periods according to their atomic number.
