CONCEPT: Rutherford’s Model of the Atom: • He bombarded the beam of alpha particles on a very thin gold foil. • While bombarding he observes the number of scattering of particles – • Most of the particles passed either un-deviated or with a very small deviation. • Some deviated by large angles • 1 out of 8000 was deflected by more than 90° • The conclusion to this deflection: • Most of the space of an atom is empty. • At the centre of an atom having a tiny positively charged particle called a nucleus. • The centre nucleus has all the mass of an atom. • The amount of positive charge at the nucleus is equal to the total amount of negative charges on all the electrons of the atom. • All the electrons revolve around the nucleus and coulomb force provide the centripetal force EXPLANATION: • After the α -particles scattering experiment, the following conclusions were made by Rutherford as regard as atomic structure: • Most of the mass (at least 99.95%) and all of the charge of an atom concentrated in a very small region is called the atomic nucleus. Therefore option 4 is correct. • The nucleus consists of proton and neutron, in which proton was first discovered by Rutherford but neutrons were later discovered by James Chadwick in 1932. • In an atom, there is maximum empty space and the electrons revolve around the nucleus in the same way as the planets revolve around the sun and the nnumber of protons and electrons inside an atom are equal under normal conditions (non-ionized).