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NCERT Solutions for Class 9 Chapter 4 Structure of the Atom


In this chapter, we get enlightened about the discovery of electrons and protons that is credited to J.J. Thomson and E.Goldstein, respectively. As per the theory by J.J.Thomson, electrons are implanted in the positive sphere. We also learn about how Neil Bohr’s model was successful as he explained how electrons are distributed in different orbits around the nucleus.

This chapter also briefs about the discovery of neutrons in an atom proposed by J.Chadwick, hence the conclusion about the existence of three sub-atomic particles i.e., protons, neutrons, and electrons. It also sheds light upon concepts such as valency, atomic number and mass number, which are essential to identify elements and their behavioural properties.

Overall, it helps us answer the basic concepts of what sets an atom apart from atoms of other elements, the indivisibility concept of atoms, representation of elements through mass number and atomic mass, as well as the basic constituents of an atom.