Test: Valence Bond Theory - Chemistry MCQ

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.

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 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.

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 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.

Valence bond theory was initially introduced by London and Heitler and was developed by Pauling and others. It’s a chemical bonding theory that explains the overlapping the atomic orbitals in order to form chemical bonds between atoms.

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 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.

Electronic configuration: Electronic configuration is the distribution of the electrons in orbitals of atoms using some basic principles like the Pauli exclusion principle and the Aufbau principle.

Ground state:

• The ground state is the state of lower energy occupied by an electron in an atomic orbital.
• The ground state is a highly stable state.

For Carbon:

• The atomic number of carbon is 6.
• The ground state electronic configuration of neutral carbon atom is 1s²2s²2p²

Excited state:

• The excited state is the state of higher energy occupied by an electron in an atomic orbital.
• The excited state is a less stable state.
• The excited-state electronic configuration of a carbon atom is 1s²2s¹2p³ i.e, the one electron from the 2s orbital gets excited to the 2p orbital by absorbing some energy.

A sigma bond is always stronger than the pi bond. As we know that the bond strength is decided by the extent of orbital’s overlapping. The extent of overlapping is more in sigma bond than in a pi-bond.