Question

How do you define the octet rule?

Answer 1

Hint: Octet rule explains the reason behind the formation of ionic or covalent bonds between different atoms in the periodic table. The octet rule can be achieved by the atoms by sharing or by transfer of electrons.

Complete answer:
- In the question it is asked to define the octet rule.
- The capacity of every atom to have eight electrons in their outer shell or valence shell by sharing of electrons or to transfer of electrons is called octet rule.
- Mostly all the compounds should show octet rule.
- If the atoms share the electrons to get octet rule then the chemical bond formed is called covalent compound.
- If the atoms donate or accept the electrons to get octet rule then the chemical bond formed is called ionic compound.
- In ionic compounds the ionic bond in between the atoms is due to difference in electronegativity values means in ionic compounds the octet rule is going to be achieved by transfer of electrons in between atoms of different electronegativity values.
- In covalent compounds the covalent bond in between the atoms is due to having the nearly same electronegativity values.

Note:
There are few limitations to octet rule.
1. Octet rule unable to explain the stability of lithium chloride, beryllium hydride and boron trichloride. That compound does not possess eight electrons in their outer shell.
2. Octet rule failed to explain the stability of the hydrogen molecule. Hydrogen has only one electron in its electronic configuration but still possesses stability.
3. In few molecules like sulphur hexafluoride and sulphuric acid the central atom has more than eight electrons, octet rule unable to explain this.