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:
We are given four chemical concepts related to chemical bonding and atomic structures. We need to identify which statement does not belong to the theoretical framework of Valence Bond Theory (VBT).

Step 2: Detailed Explanation:
Let's check the core definitions underlying each choice:
Option (A) mentions the covalent character of a bond, which is explained in VBT through localized valence orbital overlapping and sharing of electron pairs between localized atoms.
Option (B) discusses the shielding effect, which describes atomic electron shells and periodic trends, but remains compatible with atomic orbital evaluations in VBT.
Option (C) covers electron delocalization, which VBT handles via resonance contributions of individual Lewis structures.
Option (D) outlines the mathematical combination of separate atomic orbitals to generate completely new molecular orbitals that span across the whole molecule. This concept is the defining cornerstone of Molecular Orbital Theory (MOT) and stands in direct contrast to the localized atomic orbital approach of Valence Bond Theory.

Step 3: Final Answer:
The concept that is not part of valence bond theory is the combination of atomic orbitals to give molecular orbitals, which corresponds to option (D).