Question

What is octet rule? How do you appreciate role of the ‘octet rule’ in explaining the chemical properties of elements? 

(OR) 

Which rule decides whether given element is chemically stable or not? Appreciate that rule.

Answer 1

Octet rule decides whether given element is stable or not. 

Octet rule : 

1. 'The atoms of elements tend to undergo chemical changes that help to leave their atoms with eight outer shell electrons.” 

2. It was found that the elements which participate in chemical reaction get octet (or) ns² np⁶ configuration similar to that of noble gas elements.

Role of octet in chemical properties of elements : 

1. Except He remaining inert gas elements have 8 electrons in their outermost orbit. Since these elements are having stable octet configuration in their outermost orbit, they are very stable. 

2. They do not allow the outermost electrons to take part in chemical reactions. 

3. So by having octet configuration for these elements we can conclude these are chemically inertial. 

4. If any group of elements (take halogens) which contain 7 electrons in their outermost orbit, they require only 1 e^- to get octet configuration. 

5. So they try to participate in chemical reaction to get that 1 difference electron for octet configuration.

6. Similarly, Na contains 2, 8, 1 as its electronic configuration. 

7. So it loses le^- from its outermost shell; it should have 8e^- in its outer shell and get the octet configuration. 

8. Thus the octet rule helps in explaining the chemical properties of elements.