Toni Chehlarova    Yordanka Dimova

Д. Менделеев

In the middle of the 20^th century, around 60 chemical elements were known. First attempts were made to classify them on the basis of common properties. The goal was to make their studying easier and to stimulate the search for new chemical elements.

                Dmitri Mendeleev was the first to formulate the idea of periodicity. That is why it is commonly accepted that he was the first to discover the Periodic Law. In an article called “A natural system of elements and its usage to establish the properties of yet unknown elements” (1871), for the first time in the history of chemistry, the law for the mutual relation between chemical elements as “a periodic relation in the change of the properties of elements depending on their atomic weight (atomic mass)” was set out.   

 

Look for regularities in the periodic system yourself.