According to the valence bond theory(VBT), a covalent bond is formed by the overlapping of atomic orbitals containing electrons of opposite spin which pair together. However what is the physical meaning of overlapping here? Does it mean that the electrons of either orbital are now constrained to move in the region where the orbitals overlap?

Note: I know that in the case of MO theory the atomic orbitals just combine linearly(atleast approximately) to give molecular orbitals but I wonder what is the explanation that VBT provides.

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1 Answer 1


Orbitals have fuzzy boundaries so the extent of their overlapping is a matter of taste in the first place.

In the context of this linear combination approach electrons are free to use the whole combined "volume" of the molecular orbital.

  • $\begingroup$ No, you misunderstand my question. I am asking for the explanation which the Valence Bond Theory provides for the electronic behavior in an orbital overlap, not the molecular orbital theory. Besides in MO theory, the orbitals don't overlap, they combine. $\endgroup$
    – Nothing
    Mar 20 at 16:38
  • 1
    $\begingroup$ Well, then your understanding is OK - while the electrons are not "constrained" anywhere, their density is highest where the orbitals overlap. $\endgroup$
    – fraxinus
    Mar 20 at 21:01

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