Mendeleev's Periodic Table first discovered in 1869. Dmitrii Mendeleev (1834-1907) was born in Tobolsk, in Western Siberia. His chief contribution to chemistry was the establishment of the periodic system of elementsis. He present all the elements so as to show their similarities and differences.
Get help for your chemistry homework. Get facts for the elements in the periodic table.
The elements are arranged in increasing order of atomic number(Z) as you go from left to right accross the table. The horizontal rows a called periods and the vertical rows, groups.
A noble gas is found at the right hand side of each period. There is a progression from metals to non-metals across each period. Elements found in groups (e.g. alkali, halogens) have a similar electronic configuration. The number of electrons in outer shell is the same as the number of the group (e.g. lithium 2·1).
The block of elements between groups II and III are called transition metals.
These are similar in many ways; they produce colored compounds, have variable valency and are often used as catalysts. Elements 58 to 71 are known as lanthanide or rare earth elements.
These elements are found on earth in only very small amounts.
Elements 90 to 103 are known as the actinide elements. They include most of the will known elements which are found in nuclear reactions. The elements with larger atomic numbers than 92 do not occur naturally.
They have all been produced artificially by bombarding other elements with particles.
This table and the accompanying observations were first presented to the Russian Chemical Society in March 1869.