The Development of the Periodic Table

The Periodic Table of Elements, as we know it today, is the work of several scientists who contributed to its development over time. Many elements are already known to man since ancient history, such as gold, silver and tin. Then as centuries passed, other elements were discovered that by 1869, there were already 63 known elements. Although there was no need to place these elements into an organized table at that time, the scientists soon discovered certain patterns and similarities in the properties of these elements (A Brief History, 1997). Scientists then developed several classifications of these elements. It was then the beginning of the development of the periodic table of elements.

Although Mendeleev is considered the father of the Periodic Table of Elements, he was not the first scientist who devised the arrangement of the elements according to their properties.  The Periodic Table of Elements was first developed by German chemist Johann Dobereiner. He noticed similarities in properties among the known elements and then grouped them based on their similarities. In 1829, he proposed the Law of Triads, wherein the middle element has the atomic weight of the average of the other two elements (Thall, n.d.). With his Law of Triads other scientists noticed the same relationship in the elements. These were the ones not included in the triads. Thus, other elements were added to the groups while other elements were totally classified into other groups.

            Then in 1862, Alexandre Beguyer de Chancourtois published a list of all the then known elements. The elements were presented into helical graph with the elements of the same properties occupying the same line in the cylinder (Thall, n.d.). It was then the first periodic table of elements. But it was John Newlands who developed the periodicity in the properties of the elements. In 1863, he proposed the Law of Octaves, wherein the elements all showing similarities to the eight element in the table (Thall, n.d.).

            In 1869, Dimitri Mendeleeve proposed the arrangement of elements by their atomic weight and properties. In Mendeleeve’s periodic table, the elements were arranged in 17 columns, with two incomplete periods of elements followed by two complete periods. Then in 1871 he revised the arrangement with the eight columns. Although there were gaps in the arrangement, the elements showed the same similarities.

            Then in 1895 the inert gases were discovered by Lord Rayleigh and William Ramsey. The inert gases were then placed into periodic table that by 1900s the table was arranged by the atomic weight of the elements. The inert gases were later on called noble gases. 

            Then in 1911, the element proton was discovered. At that time, Henry Moseley, with the use of x-ray, was able to arrange the elements according to their atomic numbers and not by atomic masses. This showed the inconsistencies in Mendeleev’s periodic table. Thus, the elements were then arranged on the atomic numbers, according to Moseley’s Periodic Table. The modern periodic table is based on this arrangement. Then in 1940 Glenn Seaborg discovered the transuranium elements. He then arranged the lanthanide/actinide series at the bottom of Moseley’s Periodic Table of Elements. This is the Periodic Table of Elements we use today (Thall, n.d.).

Bibliography

A Brief History of the Development of Periodic Table. 1997. Western Oregon University.

Retrieved 3 March 2008 from

http://www.wou.edu/las/physci/ch412/perhist.htm

Thall, Edwin, Dr. n.d. Development of Periodic Table. Florida Community College South

Campus. Retrieved 3 March 2008 from

http://mooni.fccj.org/~ethall/period/period.htm