Test: Valence Bond Theory (May 25) - JEE MCQ

The amount of energy that is required to break a chemical bond in a molecule into individual atoms is known as bond enthalpy. 435.8 kJ mol^-1 is required to dissociate a hydrogen molecule into two hydrogen atoms.

As per the concept of valence bond theory, the partial merging of atomic orbitals id knowns as overlapping. The extent of overlapping is directly proportional to the strength of the covalent bond, i.e. it is dependent.

The electronic configuration of carbon in its ground state is given by 1s²2s²2p⁴. When it’s in an excited state, that is when it loses an electron, that would be from 2p-orbital. So the excited state’s electronic configuration is 1s²2s¹2p³.

The head-on or end to end type of overlapping is present in sigma bond. A sigma bond is a type of covalent bond. It may also be called an axial overlap. In case of the hydrogen molecule, its s-s overlapping.

A pi-bond is a type of covalent bond in which the internuclear axes of the atoms are parallel to each other and for side-wise overlapping. The bond formed here is perpendicular to the internuclear axes.

Zero overlap means that the orbitals don’t overlap at all. When there is no overlapping the bond formation doesn’t occur. As we all know that the extent of overlapping is dependent on the strength of the bond.

A positive overlap results in bond formation. When 2 p-orbitals are in phase, both the positive lobes overlap, thus creating a positive overlap and result in the bond formation, thus it is called in-phase overlap.

The molecule that is formed from the same element is known as a homonuclear molecule and the molecule that is made up of 2 atoms is called a diatomic molecule. But HCl is not a homonuclear diatomic molecule as it has different atoms.