Chapter 4

NCERT
Class 9
Science
Solutions
6. Summarise the rules for writing of distribution of electrons in various shells for the first eighteen elements.

Question:

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

Answer:

The different energy levels are written as follows—

(i) The electron in the given energy level or orbit are written according to the

formula 2n2

In the first orbit (in K orbit) 2n2 = 2 × 12 = 2 electrons

In the second orbit ( in L orbit) 2n2 = 2 × 22 = 8 electrons

In the third orbit (in M orbit) 2n2 = 2 × 32 = 18 electron

(ii) If there is an outermost orbit then the electron in it will not be more than 8.

(iii) Electrons are filled stepwise in different energy levels.

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