question_answer 42)

  Rutherford's a-particle scattering experiment showed that (i) electrons have negative charge. (ii) the mass and positive charge of the atom is concentrated in the nucleus. (iii) neutron exists in the nucleus. (iv) most of the space in atom is empty. Which of the above statements are correct? (a) (i) and (iii)                     (b) (ii) and (iv)                   (c) (i) and (iv)                     (d) (iii) and (iv)

Answer:

  (b)  Points (ii) and (iv) are correct. An atom consists of a positively charged, dense and very small nucleus which have all the protons and neutrons. Positive charge is due to protons, as neutrons have no charge. Most of the space is empty because most of the alpha particles pass straight through the gold foil without any deflection. Electrons have negative charge, it was explained by Thomson. The existence of neutron was discovered by Chadwick.