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Karnataka Board PUCPUC Science 2nd PUC Class 12
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Bonding in Coordination Compounds - Valence Bond Theory (VBT)

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Estimated time: 8 minutes
CBSE: Class 12
Maharashtra State Board: Class 12

Theory: Valence Bond Theory (VBT)

  • Proposed by Heitler and London (1927), further developed by Pauling and Slater.
  • A covalent bond is formed when half-filled valence atomic orbitals of similar energies overlap, each containing one unpaired electron.
  • Greater the overlap → stronger the bond.

Types of Orbital Overlap:

Type Description Bond Formed
Axial (Head-on) overlap Orbitals overlap along the internuclear axis Sigma (σ) bond
Sidewise (Lateral) overlap Orbitals overlap parallel to each other, perpendicular to the internuclear axis Pi (π) bond

Hybridisation & Shapes:

Hybridisation Shape Coordination No.
sp³ Tetrahedral 4
dsp² Square planar 4
sp³d Trigonal bipyramidal 5
d²sp³ Octahedral (inner) 6
sp³d² Octahedral (outer) 6

Limitations of VBT:

  • Involves a number of assumptions.
  • Does not give a quantitative interpretation of magnetic data.
  • Does not explain the colour exhibited by coordination compounds.
  • Does not give a quantitative interpretation of the thermodynamic or kinetic stabilities of coordination compounds.
  • Does not make exact predictions regarding the tetrahedral and square planar structures of 4-coordinate complexes.
  • Does not distinguish between weak and strong ligands.

Video Tutorials

We have provided more than 1 series of video tutorials for some topics to help you get a better understanding of the topic.

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Shaalaa.com | Coordination Compounds part 13 (Valence bond theory)

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Coordination Compounds part 13 (Valence bond theory) [00:16:50]
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Coordination Compounds part 13 (Valence bond theory)
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Coordination Compounds part 14 (Valence bond theory numerical)
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Coordination Compounds part 15 (Valence bond theory: limitation)
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Related QuestionsVIEW ALL [25]

Write the hybridization and shape of the following complexes:

[Ni(CN)4]2−

Using Valence bond theory, explain the following in relation to the paramagnetic complex [Mn(CN)6]3− 

  1. type of hybridization
  2. magnetic moment value
  3. type of complex – inner, outer orbital complex

The magnetic moment of [NiCl4]2− is ______.

[Atomic number: Ni = 28]

Using valence bond theory, explain the following in relation to the complexes given below:

\[\ce{[Co(NH3)6]^{3+}}\]

(i) Type of hybridisation.
(ii) Inner or outer orbital complex.
(iii) Magnetic behaviour.
(iv) Spin only magnetic moment value.

[NiCl4]2- is paramagnetic while [Ni(CO)4] is  diamagnetic though both are tetrahedral. Why? (Atomic no. Ni = 28) 

Discuss the nature of bonding in the following coordination entity on the basis of valence bond theory:

[Fe(CN)6]4−

Using valence bond theory, explain the following in relation to the complexes given below:

\[\ce{[Mn(CN)6]^{3-}}\]

(i) Type of hybridisation.
(ii) Inner or outer orbital complex.
(iii) Magnetic behaviour.
(iv) Spin only magnetic moment value.

Using valence bond theory, explain the following in relation to the complexes given below:

\[\ce{[Cr(H2O)6]^{3+}}\]

(i) Type of hybridisation.
(ii) Inner or outer orbital complex.
(iii) Magnetic behaviour.
(iv) Spin only magnetic moment value.

Related concepts

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