Molecular Orbital Theory: Why is There Mixing?

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SUMMARY

Molecular Orbital Theory explains the phenomenon of orbital mixing in diatomic molecules, particularly in the context of elements like oxygen (O) and fluorine (F) compared to boron (B), carbon (C), and nitrogen (N). In molecules such as O2 and F2, the sigma 2p bonding orbital is promoted to a higher energy level due to the mixing of s and p orbitals, which does not occur in B2, C2, or N2. Understanding the conditions under which orbital mixing occurs is crucial for predicting molecular stability and bonding characteristics.

PREREQUISITES
  • Molecular Orbital Theory fundamentals
  • Understanding of atomic orbitals and their configurations
  • Knowledge of diatomic molecules and their electronic structures
  • Familiarity with energy level diagrams for molecular orbitals
NEXT STEPS
  • Study the differences in orbital mixing between diatomic molecules using Molecular Orbital Theory
  • Explore the energy level diagrams for O2 and F2 to understand orbital promotion
  • Investigate the role of electronegativity in orbital mixing
  • Learn about the implications of orbital mixing on molecular stability and reactivity
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Chemistry students, educators, and researchers interested in molecular bonding, particularly those focusing on molecular orbital theory and its applications in understanding diatomic molecules.

semc
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Hi guys i came across molecular orbital theory and i don't understand why sometimes there is orbital mixing. For example B,C,N have no orbital mixing while O,F have orbital mixing. May i know how to know when there is orbital mixing?
 
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Perhaps my English fails me - what do you mean by "mixing"? Molecular orbitals are always linear combinations of the atomic orbitals, so in each molecule - regardless of the elements involved - atomic orbitals are "mixed" to create molecular orbitals.

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Hi borek! I meant if you are using molecular orbital theory to explain diatomic molecule like B2 the sigma 2p bonding orbital will be promoted to a higher energy level then the pi 2p bonding orbital due to mixing of s and p orbitals. But I don't understand why this does not apply for O2 or F2.
 

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