class 9 science chapter 4 important questions

  1. What are cations and anions.
  2. What is Thomson’s model of atom? What is its drawback?
  3. What are isobars? Comment on their physical and chemical properties.
  4. Give any three important characteristics of cathode rays.
  5. Give any two proofs to show that electrons are universal constituent of all atoms.
  6. What was drawback of Ruttherford’s model of atom?
  7. How was electron discovered? Explain briefly.
  8. How was proton discovered? Explain briefly.
  9. Write the important features of Bohr’s model of atom.
  10. How was neutron discovered? Explain briefly.
  11. What are isotopes? Give their important applications.
  12. Write the electronic configuration of potassium atom (Atomic number of potassium=19). What will be its valency?
  13. Write the isotopes of hydrogen and give their names.
  14. What do you think would be the observation if the alpha-particle scattering experiment is carried out using a foil of a metal other than gold?
  15. Which isotope is used in the treatment of cancer?
  16. The atom of an element has 2 electrons in the M-shell. What is its atomic number? Name the element.
  17. On the basis of Thomson’s model of an atom, explain how the atom is neutral as a whole.
  18. What do you understand by ground state and excited state of an atom?
  19. Give at least three proofs to show that electrons are present in all atoms.