VBT theory is based on the

Options

A. Knowledge of atomic orbitals and electronic configuration of elements
B. overlap criteria and the hybridisation of atomic orbitals
C. the principles of variation and superposition
D. All of the above

Answer

**Step-by-Step Text Solution:**

1. **Definition of VBT**: Valence Bond Theory (VBT) is a fundamental theory in chemistry that explains how atoms bond together to form molecules. It focuses on the concept of overlapping atomic orbitals.

2. **Overlapping Theory**: VBT is often referred to as the overlapping theory. This theory emphasizes that bonds are formed when atomic orbitals of two atoms overlap. The extent of this overlap determines the strength of the bond.

3. **Types of Bonds**: According to VBT, there are two main types of covalent bonds:
- **Sigma (σ) Bonds**: These bonds are formed when orbitals overlap along the inter-nuclear axis (the line connecting the nuclei of the two atoms). This type of bond allows for free rotation around the bond axis.
- **Pi (π) Bonds**: These bonds are formed when the overlap occurs above and below the inter-nuclear axis. Pi bonds usually occur in conjunction with sigma bonds in double or triple bonds.

4. **Bond Formation Sequence**: In the formation of multiple bonds, the sigma bond is formed first, followed by the formation of pi bonds. This sequence is crucial in understanding molecular geometry and bonding.

5. **Maximum Bonding Capacity**: VBT states that a maximum of three bonds (one sigma and two pi bonds) can be formed between two atoms. This is an important aspect of understanding the bonding capabilities of different elements.

6. **Atomic Orbitals and Hybridization**: VBT provides insights into the hybridization of atomic orbitals, which is the mixing of atomic orbitals to form new hybrid orbitals. This concept helps explain the geometry of molecules and the arrangement of bonds.

7. **Unpaired Electrons**: VBT also highlights the role of unpaired electrons in bond formation. Only unpaired electrons in atomic orbitals can participate in the formation of covalent bonds.