Chemistry holds a very important position in NEET Exam, so make your strategy accordingly with reference to topics. Here is one of the important topic for chemistry which is Classification of Elements and Periodicity in Properties, in this article you will get the overview of this topic which will help you to make notes for NEET 2020 Exam.
Classification of Elements was essential since many elements had been being found within the 19th century and the research of those elements individually was proving tough.
There have been many attempts classifying elements including ‘Dobereiner’s Triads’ and ‘Newland’s Octaves’.
German chemist Johann Wolfgang Dobereiner tried to categorize elements with related properties into groups of three elements each. These groups had been known as ‘triads’.
Dobereiner advised that in these triads, the atomic mass of the element within the center can be roughly equal to the imply of the atomic masses of the opposite two elements within the triad.
An instance of such a triad can be one containing lithium, sodium, and potassium. The atomic mass of lithium 6.94 and that of potassium is 39.10. The element in the course of this triad, sodium, has an atomic mass of 22.99 which is kind of equal to the mean of the atomic masses of lithium and potassium (which is 23.02).
The Limitations of Dobereiner’s Triads are :
English scientist John Newlands organized the 56 recognized elements in the rising order of atomic mass within the year 1866. He noticed a pattern whereby each eighth element exhibited properties much like the primary.
This similarity within the properties of each eighth element could be illustrated as figures in most of our textbooks.
Newland’s Law of Octaves states that when the elements are organized in the rising order of atomic mass, the periodicity in properties of two elements which have an interval of seven elements in between them can be related.
Limitations of Newland’s octaves are:
Russian chemist Dmitri Ivanovich Mendeleev put forth his periodic table in 1869. He noticed that the properties of elements, each physical and chemical, had been periodically associated with the atomic mass of the elements.
The Periodic Law (additionally known as Mendeleev’s Law), states that the chemical properties of elements are a periodic function of their atomic weights.
The advantages of Mendeleev’s Periodic table:
The limitations of Mendeleev’s Periodic table are: