VBT full form
What is the full form of VBT?
The full form of VBT is Valence Bond Theory. This theory was proposed by Linus Pauling. The main concept of this theory is to show that the bond that's formed between a ligand and a metal is a coordinate bond as the pairs of electrons are donated by the ligand to the metal.
Characteristics of Valence Bond Theory
For making a coordinate covalent bond, the central atom removes electrons from its s,p, and d orbitals so that the number of valencies is equal to its coordination number and thus it can form a bond with ligands.
These vacant orbitals can be termed hybrid orbitals. Also, all of these orbitals have equal energy and the same geometry.
These metals can only form a coordinate covalent bond with a ligand if a ligand has some lone pairs of electrons with it.
Ligands always have at least one pair of electrons in them. Also, Linus Pauling has divided these ligands into two parts; strong ligands and weak ligands.
The only difference between the strong ligand and weak ligand is that strong ligands can pair up with the vacant d orbitals of a metal but weak ligands cannot bind with the vacant d orbitals of a metal.
Also, there are two types of d orbitals used for hybridization and they are the inner orbital complex and outer orbital complex where the inner orbital complex is formed using inner (n-1) d-orbitals and outer orbital complex is formed using outer n d-orbitals.
There are two types of forms of a complex that can be found and they are paramagnetic and diamagnetic.
Hybridization and geometry of complexes
Coordination Number | Types of Hybridization | Geometry |
2 | sp | Linear |
3 | sp2 | Triangular planar |
4 | sp3 | Tetrahedral |
4 | sp2d | Square planar |
4 | sd3 | Tetrahedral |
5 | dsp3 | Trigonal bipyramidal |
5 | dsp3 | Square pyramidal |
6 | d2sp3 | Octahedral |
6 | sp3d2 | Octahedral |
Limitations of Valence Bond Theory
The nature of ligands cannot be explained with the help of VBT.
This theory cannot explain why the pairing of electrons cannot be done in the presence of weak ligands.
The rate of reaction and the mechanism of the reaction of the complex cannot be explained by this theory.
Frequently Asked Questions (FAQs)
CN–, and CO are examples of strong ligands, and F–, and Cl– are examples of weak ligands.
Inner (n-1) d-orbital is used for the inner orbital complex.
When all the electrons of a complex are paired then the complex is said to be diamagnetic but if any unpaired electron is present within the complex then it will be termed paramagnetic.
[CoCl4]2- is an example of a coordinate complex having sp3 hybridization and Tetrahedral geometry
No, [Fe(F)6]3- ion is an outer orbital complex.