Question

The electronegativity difference between the elements 'A' and 'B' is 3, then the bond formed in AB molecule is

• A. Ionic bond
• B. Covalent bond
• C. Sigma bond
• D. Pi bond

Answer 1

The Correct Option is A

To determine the type of bond formed in the molecule $ \text{AB} $, we need to analyze the electronegativity difference between the elements $ \text{A} $ and $ \text{B} $. The electronegativity difference is a key factor in determining the nature of the chemical bond.

1. Understanding Electronegativity Difference:
Electronegativity is a measure of an atom's ability to attract electrons towards itself in a chemical bond. The difference in electronegativity between two atoms determines the type of bond formed:
- If the electronegativity difference is small (typically less than 0.5), the bond is predominantly covalent.
- If the electronegativity difference is moderate (between 0.5 and 1.7), the bond is polar covalent.
- If the electronegativity difference is large (greater than 1.7), the bond is predominantly ionic.

In this problem, the electronegativity difference between $ \text{A} $ and $ \text{B} $ is given as 3. This value is significantly large, indicating that one atom ($ \text{A} $ or $ \text{B} $) has a much stronger attraction for electrons than the other.

2. Determining the Type of Bond:
Given that the electronegativity difference is 3, which is greater than 1.7, the bond formed in the molecule $ \text{AB} $ is predominantly ionic. In an ionic bond, one atom transfers electrons to another, resulting in the formation of positively and negatively charged ions that are held together by electrostatic forces.

3. Eliminating Other Options:
- Sigma Bond: A sigma ($ \sigma $) bond is a type of covalent bond where electron density is concentrated along the axis between the bonded atoms. While sigma bonds can be part of a covalent bond, the question specifically asks about the overall nature of the bond based on electronegativity difference, not the specific type of covalent bond.
- Pi Bond: A pi ($ \pi $) bond is another type of covalent bond where electron density is concentrated above and below the axis between the bonded atoms. Like sigma bonds, pi bonds are part of covalent bonding and do not apply here based on the electronegativity difference.
- Covalent Bond: A covalent bond forms when the electronegativity difference is small or moderate. Since the electronegativity difference here is 3, which is large, the bond cannot be classified as covalent.

4. Conclusion:
The bond formed in the molecule $ \text{AB} $, given an electronegativity difference of 3, is predominantly ionic.

Final Answer: $ {\text{(A) Ionic bond}} $