vb theory and hybridisation

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valence bond theory

• Shared Pair of Electrons: A bond is formed when two atoms share a pair of electrons.

• Atomic Orbital Overlap: The atomic orbitals from each atom overlap to create a bonding orbital, where the shared electrons reside.
  

hybridised atomic
orbitals

blend of two or more orbitals

how does orbital overlapping and bonding work?

When two atoms approach, the electrons and nucleus of
one atom interact with the electrons and nucleus of the
other.
In VB theory, we examine the energy of the electrons in the
atomic orbitals. If the energy of the system is lowered then
a bond will form, if it is raised, then a bond will not form

Interaction of two hydrogen
atoms

• Far Apart Atoms:

  • Little interaction energy when atoms are far apart.

• Approaching Atoms:

  • Interaction energy becomes negative as atoms approach, leading to stabilization and reduced potential energy.

• Equilibrium Bond Length:

  • Minimum interaction energy corresponds to the equilibrium bond length for a hydrogen molecule.

  • At this distance, there's significant overlap of the 1s orbitals of each hydrogen atom.

• Closer Than Equilibrium:

  • If atoms get closer than this distance, interaction energy increases due to repulsion between the positive nuclei.

• Chemical Bond Formation:

• a chemical bond forms from the overlap of two half-filled orbitals with spin pairing of the valence electrons.

bond types

A single bond has 1 sigma (σ) bond > end on overlapping of atomic oribitals
 A double bond has 1 sigma bond (σ) and 1
pi bond (π).
 A triple bond has 1 sigma and 2 pi bonds

sigma bond

end-on
overlap of atomic
orbitals

pi bond

side-on overlap of
atomic orbitals.

Hybridisation

• Purpose: To explain how atoms form covalent bonds and the shapes of molecules.

• Process: Atomic orbitals (like s, p, and sometimes d) combine to create hybrid orbitals.

• Result: Hybrid orbitals help form bonds in a way that leads to specific molecular shapes.

hypothetical
hybrid orbitals

Atomic orbitals obtained when two or more non-equivalent orbitals
of the same atom combine in preparation for covalent bond
formation

bond strenght

The greater the orbital overlap, the stronger the bond will
be and the shorter the bond will be