Problem 49 - A Complete Resource Book in Chemistry for JEE Main

Question

The most polar bond is (a) \(\mathrm{C}-\mathrm{F}\) (b) \(\mathrm{C}-\mathrm{O}\) (c) \(\mathrm{C}-\mathrm{Br}\) (d) \(\mathrm{C}-\mathrm{S}\)

Step-by-Step Solution

Answer

The most polar bond is C-F.

Step 1: Understanding Polarity

The polarity of a bond depends on the difference in electronegativity between the two atoms involved. The greater the difference, the more polar the bond.

Step 2: Identify Electronegativity Values

Look up the electronegativity values for the elements: Fluorine (\( F \)) is 3.98, Oxygen (\( O \)) is 3.44, Bromine (\( Br \)) is 2.96, and Sulfur (\( S \)) is 2.58. Carbon (\( C \)) has an electronegativity of 2.55.

Step 3: Compute Electronegativity Differences

Calculate the difference in electronegativity for each bond: \( \text{C}-\text{F}: 3.98 - 2.55 = 1.43 \)\( \text{C}-\text{O}: 3.44 - 2.55 = 0.89 \)\( \text{C}-\text{Br}: 2.96 - 2.55 = 0.41 \)\( \text{C}-\text{S}: 2.58 - 2.55 = 0.03 \).

Step 4: Determine the Most Polar Bond

The bond with the greatest difference in electronegativity is the most polar. \( \text{C}-\text{F} \) has the highest difference of 1.43.

Key Concepts

Electronegativity

Electronegativity is a fundamental concept in chemistry that describes an atom's ability to attract and hold onto electrons when it forms a chemical bond. Different elements have different electronegativity values, which can be found in a table of elements. Electronegativity is usually expressed on a relative scale, with fluorine being the most electronegative element at 3.98 on the Pauling scale.
Understanding electronegativity is crucial when analyzing the nature of a bond between atoms. The more electronegative an atom, the stronger its ability to attract electrons towards itself. This concept is vital when comparing how different atoms form bonds with one another, helping predict the behavior of molecules.
The differences in electronegativity values dictate exactly how electrons are shared in a bond, affecting whether a bond is polar or non-polar. In general, a greater difference in electronegativity indicates a more polar bond.

Bond Polarity

Bond polarity refers to the separation of electric charges along a bond. This occurs due to differences in electronegativity between the two bonding atoms. When analyzing bond polarity, it is important to measure the difference in electronegativity.

• A non-polar bond occurs when the difference in electronegativity is very small or negligible. This means that the electrons are shared equally.
• A polar bond, on the other hand, occurs when there is a significant difference in electronegativity between the two atoms. This causes one atom to attract electrons more strongly, inducing a dipole moment.

The presence of a polar bond in a molecule can affect its properties such as boiling point, solubility, and interaction with other molecules. Consequently, understanding bond polarity allows chemists to predict and control the behavior of molecules in different chemical environments.

Chemical Bonding

Chemical bonding is the process through which atoms combine to form molecules. This can occur via different types of bonds, with covalent bonds being one of the most common bond types.
In a simple covalent bond, atoms share electrons; however, the way in which these electrons are shared depends on the relative electronegativities of the atoms involved. The extent to which electrons are shared or transferred defines the type of bond:

• If the sharing of electrons is equal, the result is a non-polar covalent bond.
• If one atom attracts shared electrons more strongly, the bond is considered polar covalent.
• In cases where electrons are completely transferred from one atom to another, an ionic bond forms.

Each type of bond confers different properties to the resulting compound, impacting everything from molecular structure to chemical reactivity. Understanding chemical bonding is essential for grasping how different substances interact and transform in chemical reactions.