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The Fundamental Unit of Life
Describe the essential features of the model of atom proposed by E. Rutherford. How is it different from that proposed by J.J. Thomson?
E. Rutherford proposed that each atom consists of a positive nucleus around which negatively charged electrons are revolving round the nucleus just like the planets move round the sun in fixed orbits in our solar system. According to this model most of the mass is concentrated in a small central part of the atom whereas J.J. Thomson proposed that , an atom consists of a positively charged sphere and the electrons are embedded in it. He also proposed that atom is electrically neutral.
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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.
If Z = 3, what would be the valency of the element? Also, name the element.
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