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Significance and Brief History of the Development of Periodic Table

The elements are the basic units of all types of matter. Only 31 elements were known in 1800. Now more than 105 elements are known.It is impossible to remember the properties of each element and its compounds. Therefore, many attempts have been made to classify elements into fewer groups. The purpose of the classification has been to make the study of the chemistry of elements and their compounds easier. Dmitri I. Mendeleev (1834-1907) developed the periodic table. From the relationships embodied in the table, he predicted the existence as well as properties of elements then unknown. These predictions came out to be amazingly accurate.  During the course of time, the basis of classification changed from atomic mass to atomic number.


The study of chemistry has become simple on the basis of the modern classification of elements. Now, by knowing the properties of one element of a group, it is possible to predict the properties of the other members. One need not remember all the properties of elements or their compounds. All one has to do is to know the trends of properties in a group and in a period of the periodic table.

Brief History of the Development of Periodic Table
In 1829, Döbereiner suggested that elements could be arranged in groups of three i.e. triads, in which the atomic weight of the middle element was nearly the mean of the atomic weights of the other two. However, only a limited number of elements could be grouped into these triads.


Table 5.1 Dobereiner's Triads of Elements




Mean atomic weight

Lithium (7)



(7+ 39)/2 = 23





Calcium (40)

Strontium (87.5)

Barium (137.5)

(40 +137.5)/2 = 88.75





Phosphorus (31)

Arsenic (76)

Antimony (120)

(31 + 120)/2 = 75.5





Sulphur (32)

Selenium (79)

Tellurium (127.5)

(32+ 137.5)/2 = 79.25





Chlorine (35.5)

Bromine (80)

Iodine (127)

(35.5 + 127)/2 = 81.25





John A.R. Newlands, in 1865-1866, reported that if the elements were arranged in order of their increasing atomic weights, the eighth element starting from a given one, possessed properties similar to the first, like the eighth note in an octave of music. He called it the law of octaves. It worked well for the lighter elements but failed when applied to heavier elements.

In 1869, J. Lothar Meyer in Germany and Dmitir I. Mendeleev in Russia, working independently, gave a more detailed and accurate relationship among the elements. Lother plotted atomic volumes (=atomic mass/volume) versus atomic weights of elements and obtained a curve. He pointed out that, elements occupying similar positions in the curve possessed similar properties.

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