Kossel-Lewis Approach To Chemical Bonding
Chapter Name : Chemical Bonding And Molecular Structure |
Sub Topic Code : 102_11_04_02_06 |
Topic Name : Kossel-Lewis Approach To Chemical Bonding |
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Sub Topic Name : Limitations of Octet Rules |
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Introduction
• The octet rule, though useful, is not universal. • It applies mainly to the second period elements of the periodic table. • In some compounds, the number of electrons surrounding the central atom is less than eight. E.g. LiCl, BeH2 and BCl3. • In molecules with an odd number of electrons like nitric oxide, NO and nitrogen dioxide, NO2, octet rule is not followed by all atoms. • In a number of compounds, elements beyond the third period have more than eight valence electrons around the central atom.
Pre-Requisites:
Octet rule
Real Life Question:
Do all atoms have 8 electrons in their valence to form bonds?
Key Words / FlashCards
| Key Words | Definitions (pref. in our own words) |
|---|---|
| octet | Octet is the presence of 8 electrons in the valence shell of atoms in a molecule. |
Learning aids / Gadgets
| Gadgets | How it can be used |
|---|---|
| Pebbles and sticks | Make Lewis structures by using pebbles and sticks for sulfur dichloride. |
Real life uses :
Many molecules have to disobey the octet rule for making their structures work.
Practical examples around us
| Examples | Explainations |
|---|---|
| Chalk | Chalk is made of calcium carbonate, carbonate being a polyatomic ion. |
What you learn in Theory:
There are many exceptions of octet rule.
What you learn in Practice:
Octet rule is not universal.