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

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

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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 in an orbit of n = 1 given by

2n2 = 2 × 1 2 = 2

Similarly, for second orbit, it is 2n2 = 2 × 2 2 = 8

For third orbit, it is 2n2 = 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 step wise manner i.e., the outer shell is not occupied with electrons unless the inner shells are completely filled with electrons.

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

→ If n gives the number of orbit or energy level, then 2n2 gives the maximum number of electrons possible in a given orbit or energy level. Thus,

First orbit or K-shell will have 2 electrons,

Second orbit or L-shell will have 8 electrons,

Third orbit or M-shell will have 18 electrons.

→ If it is the outermost orbit, then it should have not more than 8 electrons.

→ There should be step-wise filling of electrons in different orbits, i.e., electrons are not accompanied in a given orbit if the earlier orbits or shells are incompletely filled.