Historical Development of the Periodic Table

4.1

Development of Periodic Table of Elements

The chemists try to develop and make a generalisation of the element by classifying it into a certain characteristic.
The classification will enable scientists ;
- to generalise the chemical and physical properties.
- to predict the position of an element.
- to identify and compare elements from a different group.
- to predict chemical and physical properties.

Scientist	Description
Antoine Lavoisier	Group the element into four groups, which are gas, metal, non-metal and metal oxide. Light and heat are included in the classification. Some elements are in the wrong group because of different chemical properties.
Johann W. Dobereiner	Group the elements into three which are called as a triad. Discovers the relationship between the relative atomic mass (RAM) of the element in each triad. However, this relationship does not apply to most of the other elements.
John Newlands	Arranged the elements in order of increasing nucleon number. The chemical properties of every eight elements are similar, and it is known as the law of octaves. The classification was a failure because of: The law of octaves was only accurate for the first 16 elements. There was no position allocated for elements yet to be discovered.
Lothar Meyer	Calculated the volume of an atom by dividing the mass with the density of the element.
Dmitri Mendeleev	Arranged the elements in order of increasing atomic mass. The arrangement followed the atomic mass but not the chemical properties
Henry G.J. Moseley	Bombarded different elements with high energy electrons and measured the frequency of the X-ray emitted by the element. Plotted the square root of the frequency of the X-ray against the proton number. Managed to get a straight line graph.