Polar and Non Polar Covalent Bond – Chemistry Class 9

Polar and Non Polar Covalent Bond — Class 9 Chemistry Lecture Summary

Lecture Overview

This lesson adds a critical nuance to covalent bonding by introducing Polarity. The teacher explains that "sharing" electrons does not always mean sharing them equally, leading to the division between Polar and Non-Polar bonds.

Main Concepts Explained by the Teacher

He introduces Electronegativity (the power of an atom to attract shared electrons). If two identical atoms bond (like $H_2$ or $Cl_2$), they pull equally, creating a Non-Polar Covalent Bond. However, if two different atoms bond (like $HCl$), the more electronegative atom (Chlorine) pulls the electrons closer to itself, gaining a partial negative charge ($\delta^-$), leaving Hydrogen with a partial positive charge ($\delta^+$). This creates a Polar Covalent Bond.

Important Definitions and Terms

• Electronegativity: The tendency of an atom to attract the shared pair of electrons towards itself.
• Non-Polar Covalent Bond: A bond where electrons are shared equally between two atoms (Electronegativity difference is roughly 0 to 0.4).
• Polar Covalent Bond: A bond where electrons are shared unequally, creating partial charges (Electronegativity difference is roughly 0.5 to 1.7).

Key Points and Lists from the Lecture

• Fluorine, Oxygen, and Nitrogen are highly electronegative.
• Water ($H_2O$) is a highly polar molecule, which is why it is the universal solvent.
• Polar molecules act like tiny magnets with positive and negative poles.

What Students Should Remember

Actually, remembering the Delta ($\delta$) symbol is crucial. You must use $\delta^+$ and $\delta^-$ to show partial charges in polar bonds. If you use a full $+$ or $-$ sign, the examiner will mark it wrong because full charges only exist in Ionic bonds, not covalent ones!

Textbook, Notes, and Practice Links

• Textbook: Chemistry Full Textbook
• Video Notes: Notes for this Lecture

Final Recap & Board Exam Notes

By understanding polarity, students learn why oil and water don't mix (water is polar, oil is non-polar). This concept is the key to understanding solubility, boiling points, and the physical properties of all liquids.

• If you're studying for the Punjab Textbook Board (PTB) chemistry exams, this summary is gold.*

Honestly, this covers all the key MCQs for the 9th class board exams. Learn it well.