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 center of an atom having a tiny positively charged particle called a nucleus.
- The center 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:
- 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 a number of protons and electrons inside an atom are equal under normal conditions (nonionized). Therefore option 1 is correct.
- The nucleus is positively charged and its diameter (size) is of the order of
10−15m≈1 Fermi. Therefore option 2 is correct.
- The concept of electrons move in a circular path of fixed energy called orbits was put forward by Bohr and not derived from Rutherford's scattering experiment. Therefore option 3 is incorrect.
- 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.