Electronic Configuration


 
 
Concept Explanation
 

Electronic Configuration

Distribution of electrons in different orbits (shells): The distribution of electrons into different orbits of an atom was suggested by Bohr and Bury. For writing the number of electrons in different levels or shells, some rules are followed. These are:

1.  The maximum number of electrons present a shell is given by the formula 2n^2 where, n is the orbit number or energy level 1, 2, 3….Therefore, the maximum numbers of electrons in different shells are as follows:

  • 1st orbit or K-shell = 2 x (1)^2 = 2    2nd orbit or L-shell =2 x (2)^2 =8
  • 3rd orbit or M-shell =2 x(3)^2= 18    4th orbit or N-shell =2 x (4)^2= 32 and on.
  • 2.    The maximum number of electrons that can be accommodated in the outermost orbit is 8. This is a very important rule and is sometimes called the octet rule. According to this rule, the presence of 8 electrons in the outermost shell makes the atom very stable.3.    Electrons are not accommodated in a given shell, unless the inner shells are filled (i.e. the shells are filled in a stepwise manner).

    Sample Questions
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    Question : 1

    The maximum electron present in N-shell are ____________.

    Right Option : C
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    Question : 2

    Among the noble gases which gas does not have an octet configuration?

    Right Option : B
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    Question : 3

    The difference in the number of electrons between K and L and L and M shells is the same for an atom of element X (M shell is the valence shell) and the difference value is the number of valence electrons in the M shell of the other element Y.  Give the electronic configurations of their stable ions.

    Right Option : C
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