Structure of Atom (Introduction) || for Class 9 in Hindi

In this Science (Chemistry) video in Hindi we introduced the chapter, Structure of Atom for class 9. This is a topic from Chapter 4 of NCERT Science.

For a significant period of time we thought that atoms are indivisible. But the story changes with discovery of electrons. Several scientists including J J Thomson played a huge role on that. Thomson found out the mass to charge ratio of an electron. Then he took three possibilities into consideration

➣ Each negatively-charged electron was paired with a positively-charged particle that followed it everywhere within the atom.
➣ Negatively-charged electrons orbited a central region of positive charge having the same magnitude as the total charge of all the electrons.
➣ The negative electrons occupied a region of space that was uniformly positively charged.

But he published the last one.

Eventually, Ernest Rutherford, one of the research assistant of Thomson, conducted an experiment, known as Rutherford alpha scattering experiment, with Hans Geiger and Ernest Marsden. The result they found led to the conclusion that
➣ Much of an atom's positive charge is concentrated in a relatively tiny volume at the centre of the atom, known today as the nucleus.
➣ Negatively charged electrons revolve around the nucleus in circular paths (orbits). Electrons are held to nucleus by a strong electrostatic force of attraction.

Then came another assistant of Thomson, Niels Bohr. He gave a better atomic model where he concluded that
➣ The electron is able to revolve in certain stable orbits around the nucleus without radiating any energy. The electron cannot have any other orbit in between the discrete ones.

Then Rutherford discovered proton and one of his students, James Chadwick discovered neutron. And conclusions were taken that the nucleus is made of protons and neutrons and electrons revolve in orbits around the nucleus.

Then came the quantum mechanical model of atom.

How are Electrons Distributed in Different Orbits (Shells) ?
➣ The maximum number of electrons present in a shell is given by the formula 2n^2.
➣ The maximum number of electrons that can be accommodated in the outermost orbit is 8.

In this chapter (Chapter 4 - Structure of Atom, Science, Class 9th, NCERT) we will be going to explained all those concepts and laws with details.

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🔴 Click here to watch the whole playlist on Chapter 4 : 'Structure of Atom' for Class 9 :

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