Question -
Answer -
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 ‘2n2’, where ‘n’ is the orbit number or energy level index (n = 1, 2, 3…).
The maximum number of electrons present inan orbit of n =1 is given by 2n2 = 2×12 =2
Similarly, for second orbit, it is 2n2 =2×22 = 8
For third orbit, it is 2n2 =2×32 = 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.