most important questions for class 9th chapter 4

  1. Give two examples from everyday life where we use cathode ray tubes.
  2. What are the actual values of charge and mass of the electron?
  3. Define electron.
  4. Name the scientist who showed the existence of protons in atoms?
  5. What are canal rays?
  6. Define proton.
  7. In Rutherford’s scattering experiment, some but very few alpha particles are deflected back. What does it prove?
  8. Why are Bohr’s orbits called stationary states?
  9. What are the symbols used to represent different orbits? Arrange them in order of energy.
  10. What do you mean by ground state, of an atom?
  11. What do you mean by excited state, of an atom?
  12. Who discovered neutron and when?
  13. Define neutron,.
  14. What is the maximum number of electrons that can be present in the outermost shell?
  15. What do you mean by valence electrons?
  16. What is valence shell?
  17. What do you mean by valency, of an element?
  18. What are isotopes? Give one example.
  19. Represent the three isotopes of hydrogen and give their names.