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Atomic Structure

 ATOMIC STRUCTURE

name of the chapter:  Atomic Structure

Content Provider: FIITJEE

Lecturer from FIITJEE


NCERT content:

The existence of atoms has been proposed since the time of early Indian and Greek philosophers (400 B.C.) who were of the view that atoms are the fundamental building blocks of matter. According to them, the continued subdivisions of matter would ultimately yield atoms that would not be further divisible. The word ‘atom’ has been derived from the Greek word ‘a-tomio’ which means ‘uncuttable or ‘non-divisible. These earlier ideas were mere speculations and there was no way to test them experimentally. These ideas remained dormant for a very long time and were revived again by scientists in the nineteenth century. The atomic theory of matter was first proposed on a firm scientific basis by John Dalton, a British school teacher in 1808. His theory called Dalton’s atomic theory, regarded the atom as the ultimate particle of matter (Unit 1). In this unit, we start with the experimental observations made by scientists towards the end of nineteenth and beginning of the twentieth century. These established that atoms can be further divided into subatomic particles, i.e., electrons, protons, and neutrons— a concept very different from that of Dalton. The major problems before the scientists at that time were: 

• to account for the stability of atoms after the discovery of sub-atomic particles

• to compare the behavior of one element from other in terms of both physical and chemical properties

*to explain the formation of different kinds of molecules by the combination of different atoms and

, • to understand the origin and nature of the characteristics of electromagnetic radiation absorbed or emitted by atoms

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