Question

Valence bond theory of Pauling and Slater accounts for \(\ldots \ldots \ldots\) characteristics of covalent bond. (1) strength (2) directional (3) both (4) none of these

Short answer

Option (3) both.

Step-by-step solution

Identify the Concept

Determine what Valence Bond Theory (VBT) of Pauling and Slater addresses in terms of covalent bonds.

Analyze the Options

Understand each option given: strength of the bond, directional nature of the bond, both characteristics, or none of these characteristics.

Relate VBT to the Options

Valence Bond Theory explains the formation of covalent bonds where atomic orbitals overlap. This overlap provides both strength and directionality to the bonds.

Select the Correct Answer

Since Valence Bond Theory accounts for both the strength and directionality of covalent bonds, the correct option is (3) both.

Key concepts

Covalent Bond Strength

Valence Bond Theory (VBT) helps us understand the strength of covalent bonds. A covalent bond forms when two atoms share their electrons. This sharing happens because their atomic orbitals overlap. The stronger the overlap, the stronger the bond. This is because more electron density is concentrated between the two nuclei, pulling them together more strongly. Think of it like two people holding hands—the firmer the grip (overlap), the harder it is to pull them apart (stronger bond).
In summary, under VBT:

• Overlapping orbitals lead to bond formation
• Greater overlap results in stronger bonds
• Stronger bonds have more shared electron density between nuclei

Directional Nature of Bonds

Another key idea in Valence Bond Theory is the directional nature of bonds. Unlike ionic bonds that occur in all directions, covalent bonds are directional. This directionality arises from the specific shapes and orientations of the atomic orbitals involved in the overlap. For example, a p-orbital has a dumbbell shape, causing the bond to have a preferred direction along the axis of the orbital. This is why molecules like water (H₂O) and methane (CH₄) have specific geometries. Directional bonds lead to:

• Predictable molecular shapes
• Defined bond angles
• Specific chemical properties based on geometry

Pauling and Slater

Linus Pauling and John C. Slater were pivotal in developing Valence Bond Theory. They introduced the idea that atomic orbitals could mix or hybridize to form new, more effective bonding orbitals. This hybridization explains the directed formation of bonds, leading to the exact geometries observed in molecules. Pauling and Slater's contributions can be understood as:

• Explaining how orbital overlap creates strong bonds
• Demonstrating the directional nature of covalent bonds
• Introducing hybridization to account for molecular shapes

This theory helps predict and explain the shapes and strengths of molecules, making it easier for chemists to understand and manipulate chemical structures.