Available Answers

1. 1.

   State the main postulaes of - Dalton's atomic theory. Explain how the modern atomic theory contradicted Dalton's atomic theory.

2. 2.

   With reference to the discovery of the structure of an atom, explain in brief - William Crookes experiment for the discovery of cathode rays, followed by - J. J. Thomsons. State which sub-atomic particle was discoverd from his experiment.

3. 3.

   Explain in brief - Goldstein's experiment which led to the discovery of the proton and - Lord Rutherford's experiment which led to the discovery of the atomic nucleus.

4. 4.

   'Electrons revolve around the nucleus in fixed orbots or shells called energy levels'. State how these energy levels are represented.

5. 5.

   Draw a neat labeled diagram representing an atom. Name the three sub-atomic particles in the atom & represent them symbolically showing the mass & charge of each. State where the sub-atomic particles are present in the atom.

6. 6.

   Define the term - 'mass number' of an atom. If an atom 'B' has mass number 35 & atomic number 17, state the number of protons, electrons and neutrons it contains.