Anand Classes offers well-structured Class 11 Chemistry notes on Non-Polar and Polar Covalent Bonds covering the concept of bond polarity, electronegativity difference, and factors affecting polarity of bonds. Understand how electron sharing leads to polar or non-polar covalent bonds, learn with real-life examples, and practice important short answer questions and MCQs for NEET, JEE, and CBSE board exams. These concise notes make complex concepts easy to revise and perfect for exam preparation. Click the print button to download study material and notes.
What is Polarity of Bonds?
A 100% ionic bond or a 100% covalent bond represents an ideal situation. However, in reality, no bond is completely ionic or completely covalent. Even in covalent bonds (e.g., $H_2$), there is always some ionic character.
What is a Non-Polar Covalent Bond?
- When a covalent bond is formed between two similar atoms, the shared pair of electrons is equally attracted by both nuclei of two atoms.
- The electron pair is exactly midway between the two nuclei of two atoms.
- Such a bond is called a non-polar covalent bond.
Examples: $H_2$, $O_2$, $N_2$, $Cl_2$, $F_2$
What is a Polar Covalent Bond?
- When covalent bonds form between different atoms, their electronegativities differ.
- The shared pair of electrons is displaced towards the more electronegative atom.
Example: Hydrogen chloride ($HCl$)
- Electronegativity of $Cl = 3.0$
- Electronegativity of $H = 2.1$
- Due to the larger electronegativity of chlorine, the bonding pair will be attracted more towards chlorine atom.
As a result:
- $Cl$ acquires a partial negative charge ($\delta^-$)
- $H$ acquires a partial positive charge ($\delta^+$)
This creates two poles in the molecule, making it a polar molecule. The bond is called a polar covalent bond.
What Determines the Degree of Polarity?
- The magnitude of electronegativity difference reflects the degree of polarity.
- Greater the difference in the electronegativities of the atoms forming the bond, greater will be the charge separation and hence greater will be the polarity of the molecule.
- Greater the difference in electronegativity → greater charge separation → stronger polarity.
Examples of polar molecules: $BrCl$, $H_2O$, $HF$, $HCl$
Short Answer Conceptual Questions (SAT)
Q1. Define non-polar covalent bond with examples.
Answer:
A covalent bond formed between two identical atoms with equal electronegativity is called a non-polar covalent bond.
Examples: $H_2$, $Cl_2$, $O_2$, $N_2$, $F_2$
Q2. What is a polar covalent bond? Give an example.
Answer:
When a covalent bond forms between two different atoms with different electronegativities, the shared electron pair shifts towards the more electronegative atom. This bond is called a polar covalent bond.
Example: In $HCl$, $Cl$ (EN = 3.0) attracts electrons more than $H$ (EN = 2.1), so $Cl$ becomes $\delta^-$ and $H$ becomes $\delta^+$.
Q3. State the relation between electronegativity difference and bond polarity.
Answer:
The greater the electronegativity difference between two bonded atoms, the greater is the bond polarity.
Multiple Choice Questions (MCQs)
Q1. Which of the following molecules is non-polar?
(a) $HF$
(b) $H_2O$
(c) $Cl_2$
(d) $HCl$
Answer: (c) $Cl_2$
Explanation: $Cl_2$ is formed between two identical atoms with no electronegativity difference → non-polar.
Q2. Which bond is most polar?
(a) $H—F$
(b) $H—Cl$
(c) $H—I$
(d) $H—Br$
Answer: (a) $H—F$
Explanation: Fluorine has the highest electronegativity, so $H—F$ has the greatest electronegativity difference and strongest polarity.
Q3. In $HCl$, partial charges are represented as:
(a) $H^{\delta^-}—Cl^{\delta^+}$
(b) $H^{\delta^+}—Cl^{\delta^-}$
(c) $H^+—Cl^-$
(d) No charge separation
Answer: (b) $H^{\delta^+}—Cl^{\delta^-}$
Explanation: Chlorine is more electronegative, so it gets $\delta^-$; hydrogen gets $\delta^+$.
Assertion-Reason Questions
Q1.
Assertion (A): $H_2O$ is a polar molecule.
Reason (R): Oxygen is more electronegative than hydrogen, and the bent geometry of $H_2O$ gives a net dipole moment.
- (a) A and R both true, R is correct explanation of A
- (b) A and R both true, R not correct explanation of A
- (c) A true, R false
- (d) A false, R true
Answer: (a)
Q2.
Assertion (A): $Cl_2$ molecule is non-polar.
Reason (R): Both chlorine atoms have the same electronegativity, so the electron pair is equally shared.
Answer: Both A and R are true, and R is the correct explanation of A.
Q3.
Assertion (A): The polarity of $H—F$ bond is greater than that of $H—I$.
Reason (R): Fluorine is more electronegative than iodine.
Answer: Both A and R are true, and R is the correct explanation of A.
Case Study Question
Passage:
Polarity of a covalent bond depends on the difference in electronegativity of the bonded atoms. In a non-polar bond (e.g., $Cl_2$), the electron pair is equally shared. In a polar bond (e.g., $HCl$), chlorine attracts electrons more strongly than hydrogen, creating partial charges: $H^{\delta^+}$ and $Cl^{\delta^-}$. The polarity of bonds leads to the formation of polar molecules like $H_2O$ and $HF$. The greater the electronegativity difference, the higher the bond polarity.
Questions:
- Why is $Cl_2$ non-polar?
- Which end of $HCl$ is $\delta^-$?
- Arrange the following in increasing bond polarity: $H—I$, $H—Br$, $H—Cl$, $H—F$.
Answers:
- Because both chlorine atoms have equal electronegativity, electrons are shared equally.
- Chlorine end is $\delta^-$.
- Order of polarity: $H—I < H—Br < H—Cl < H—F$.