#### Question

Summarize the rules for writing of distribution of electrons in various shells for the first eighteen elements.

#### Solution

The rules for writing of the distribution of electrons in various shells for the first eighteen elements are given below.

(i) The maximum number of electrons that a shell can accommodate is given by the formula ‘2*n*^{2}’, where ‘*n*’ is the orbit number or energy level index (*n* = 1, 2, 3…).

The maximum number of electrons present in an orbit of *n* = 1 is given by 2*n*^{2} = 2×1^{2} = 2

Similarly, for second orbit, it is 2*n*^{2} = 2×2^{2 }= 8

For third orbit, it is 2*n*^{2} = 2×3^{2} = 18

And so on……

(ii) The outermost orbit can be accommodated by a maximum number of 8 electrons.

(iii) Shells are filled with electrons in a stepwise manner i.e., the outer shell is not occupied with electrons unless the inner shells are completely filled with electrons.