Dobernier Triad
In 1829, Dobernier attempted the first-ever classification of elements. He placed 3 elements in a group and stated that the mass of the middle element is equal to the arithmetic mean of the other two elements. He made 3 such groups. The group formed by him is shown below:
Li | Ca | Cl |
Na | Sr | Br |
K | Ba | I |
In the first group, the atomic mass of Li is 7 and K is 39. If we find the mean of atomic masses of Li and K it will be (7 + 39)/2 = 46/2 = 23 which is the atomic mass of Sodium. This property was followed in the three groups formed.
Drawbacks of Dobernier’s Triad
The drawbacks of the Dobernier’s Triads are discussed below,
- Dobernier could only form three such triads out of 30 elements that were known at that time.
- Dobernier Triad was not applicable to very low or very high atomic mass elements
- In the case of F, Cl, and Br, the rule of arithmetic mean is not valid, although F, Cl, and Br are placed in the same order in the modern periodic table.
Periodic Classification of Elements
Periodic Classification of Elements refers to the arrangement of elements on the basis of the periodic repetition of their properties. It means the elements which exhibit similar properties on a regular interval are placed in the same group.
In this article, we will learn about, History of the Classification of Elements, various ways to classify elements, their drawbacks, and others in detail in this article.