Concept: Valence Bond Theory (VBT) describes the formation of chemical bonds through the overlapping of atomic orbitals. It explains the shapes of molecules and the strength of bonds (sigma vs. pi).

Why (D) is incorrect:

According to Valence Bond Theory, p-orbitals can participate in both head-on (axial) overlapping to form sigma bonds and sideways (lateral) overlapping to form pi bonds. For example, in the formation of a sigma bond between two p-orbitals (e.g., in F₂ molecule), the p-orbitals overlap axially. Sideways overlapping of p-orbitals forms pi bonds, as seen in C=C or C≡C bonds.

Option Analysis:

• A) A sigma bond is stronger than π-bond: This is a correct statement. Sigma bonds are formed by head-on overlap, leading to greater overlap and stronger bonds compared to pi bonds formed by sideways overlap.
• B) s-orbitals never form π-bonds: This is a correct statement. s-orbitals are spherical and can only overlap axially (head-on) to form sigma bonds. They cannot undergo sideways overlap.
• C) There can be only one sigma bond between two atoms: This is a correct statement. Between any two atoms, the first bond formed is always a sigma bond. Any subsequent bonds (in double or triple bonds) are pi bonds.
• D) p-orbitals always have only sideways overlapping: This is an incorrect statement. p-orbitals can undergo both head-on (axial) overlap to form sigma bonds and sideways (lateral) overlap to form pi bonds.

Correct Answer: (D)