CBSE Class 9 Answered

RUTHERFORD’S NUCLEAR ATOMIC MODEL

Rutherford in 1911, introduced the concept of a nucleus being present in the atom. Hence it is known as the nuclear atomic model.

He conducted an experiment in which positively charged particles (called alpha particle) were shot at a very thin piece of gold foil in vacuum.

Observations and conclusions are as follows:

a)    Most of the particles passed through the gold foil without any deflection.

Conclusion-

As most of the particles passed without deflection, it indicates that the most of the space in the atom must be empty.

b)    Some particles were deflected through small and large angles.

Conclusion-

As  particles deflected through small angles, it indicates that there is a ‘centre of

positive charge’ in an atom. This center repels the positively charged alpha particles

and deflects them from their original path.

c)    A very small fraction of the alpha particles were bounced back to their original path.

Conclusion-

As very small fraction of particles bounced back, it shows that the nucleus is very dense and hard which does not allow the alpha particles to pass through it.

 Rutherford’s ?-particle scattering experiment provides the following important information about the nucleus of the atom:

1. Nucleus of an atom is positively charged.
2. Nucleus of an atom is very dense and hard.
3. Nucleus of an atom is very small as compared to the size of the atom as a whole.