Question

Which of the following concepts is NOT of valence bond theory?

• A. Covalent character of bond
• B. Shielding effect of electrons
• C. Delocalisation of electron over the two nuclei
• D. Combination of atomic orbitals to give molecular orbitals

Hint:

Look closely at the explicit wording in the options. The phrase "molecular orbitals" is a direct giveaway for Molecular Orbital Theory (MOT). Since the question asks for a concept that is NOT part of Valence Bond Theory, this choice stands out instantly.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
Four bonding concepts are given; we must pick the one that falls outside Valence Bond Theory (VBT).

Step 2: Detailed Explanation:
(A) Covalent character is explained in VBT via localized orbital overlap and electron pair sharing. (B) Shielding effect concerns atomic shells and periodic trends, compatible with VBT's atomic orbital treatment. (C) Electron delocalization is handled in VBT through resonance among canonical structures. (D) Combining atomic orbitals to generate delocalized molecular orbitals spanning the entire molecule is the foundational principle of Molecular Orbital Theory (MOT), directly opposing VBT's localized bond approach.

Step 3: Final Answer:
The concept not belonging to VBT is the combination of atomic orbitals to give molecular orbitals, option (D).