Why is that certain atoms are radioactive while many others are not?
If the number of neutrons exceeds the number of protons in the atom, then becomes unstable. For example, 
containing 6 protons and 6 neutrons is stable while 
which contains 6 protons and 8 neutrons is unstable and is radioactive.
Compare the properties of electron, proton and neutron.
What are the limitations of J.J. Thomson’s model of atom?
What are the limitations of Rutherford model of the atom?
Describe Bohr's model of the atom ?
Compare all the proposed models of an atom given in this chapter.
Summarize the rules for writing of distribution of electrons in various shells for the first eighteen elements.
Define valency by taking examples of silicon and oxygen.
Explain with examples, (i) Atomic number, (ii) Mass number, (iii) Isotopes, and (iv) Isobars. Give any two uses of isotopes also.
Na+ has completely filled K and L-shells. Explain.
Mock Test Series
