-
Starting the Periodic table
German chemist Johann Dobereiner started grouping elements based on there similarities with eachother. Hence triads -
First Periodic Table
It was a 19th century geologist who first recognized periodicity in the elements. Alexandre Beguyer de Chancourtois (1820-1886).
Using geological terms and published without the diagram, de Chancourtois ideas were completely ignored until the work of Mendeleev. -
Law of Octaves
English chemist John Newlands (1837-1898), having arranged the 62 known elements in order of increasing atomic weights, stating that after interval of eight elements similar properties reappeared. -
Mendeleev's Periodic Table
In 1869, Russian chemist Dimitri Mendeleev proposed arranging elements by atomic weights and properties. Mendeleev's periodic table contained 17 columns with two partial periods of seven elements each followed by two nearly complete periods.
In 1871 Mendeleev revised the 17-group table with eight columns This table exhibited similarities not only in small units such as the triads, but showed similarities in an entire network of vertical, horizontal, relationships. The table contained gaps. -
Noble Gases
Lord Rayleigh and William Ramsey greatly improved the periodic table by discovering the "inert gases." In 1895 Rayleigh reported the discovery of a new gaseous element named argon. This element was chemically inert and did not fit any of the known periodic groups. -
Moseley's Periodic Law
Soon after Rutherford's experiment of discovering the proton in 1911, Henry Moseley subjected elements to x-rays. He was able to derive the relationship between x-ray frequency and number of protons. When Moseley arranged the elements according to increasing atomic numbers and not atomic masses, some of the inconsistencies associated with Mendeleev's table were eliminated. The modern periodic table is based on Moseley's Periodic Law -
Modern Periodic Table
The periodic table we have now
