Questions and Answers
Is F2 paramagnetic or diamagnetic?
Is O2 paramagnetic or diamagnetic?
Is N2 diamagnetic or paramagnetic?
Is C2 diamagnetic or paramagnetic?
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Is B2 diamagnetic or paramagnetic?
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Why do the energy levels of sigma 2p and pi 2p switch for C2 and B2?
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What is orbital mixing (hybridization)?
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What is the important result of orbital mixing?
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What is the trend for the 2s-2p gap across the period?
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For what elements is orbital mixing negligible?
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For what elements is orbital mixing important?
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What is the difference when constructing a heteronuclear diatomic molecule's orbital diagram and a homonuclear diatomic molecule's orbital diagram?
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For the MO diagram of a heteronuclear diatomic, which element's atomic orbitals are lower in energy?
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Why is the bond polar in the bonding orbital?
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What is the bond order of HF?
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What is the bond order of CO?
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Why are not all combinations of atomic orbitals not possible?
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What are symmetry adapted orbitals?
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Which orbitals on oxygen can interact with the in-phase combination of hydrogen orbitals in H2O?
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Which orbitals on oxygen can interact with the out-of-phase combination of hydrogen orbitals in H2O?
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Which hydrogen orbitals does 2px interact with?
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How many molecular orbits result from the in-phase combination of hydrogen atoms?
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How many molecular orbits result from the out-of-phase combination of hydrogen atoms?
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What are the lone pairs for the molecular orbitals of H2O?
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How do we use MO theory to predict the structures of molecules?
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Why is water bent?
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Study Notes
Molecular Properties
- F2 is diamagnetic.
- O2 is paramagnetic.
- N2 is diamagnetic.
- C2 is diamagnetic, although molecular orbital diagrams indicate it can be paramagnetic.
- B2 is paramagnetic, despite appearing diamagnetic in molecular orbital diagrams.
Energy Levels and Orbital Mixing
- The energy levels of the sigma 2p and pi 2p orbitals switch in C2 and B2 due to the pi orbital's energy being relatively constant while the sigma orbital energy increases from F2 to B2, crossing above pi at N2.
- Orbital mixing, or hybridization, occurs when an orbital interacts with multiple orbitals, creating molecular orbitals with varying Pz and s character.
- Important outcome of orbital mixing is that the sigma 2p orbital no longer maintains pure p character, with its energy possibly exceeding that of pi 2p.
Trends and Molecular Diagrams
- The gap between 2s and 2p orbitals increases across the period due to more effective penetration of the 2s orbital compared to the 2p.
- Orbital mixing is negligible for O2 and F2, but is significant for N2, C2, and B2.
- Heteronuclear diatomic molecular orbital diagrams differ from homonuclear diagrams as they account for different energy levels of the atomic orbitals of the constituent elements.
Bond Characteristics
- In a heteronuclear diatomic molecule, the more electronegative element's atomic orbitals are lower in energy.
- Bonds are polar in bonding orbitals when electron pairs are unequally shared, leading the molecular orbitals to be more similar to the atomic orbitals of the closest energy.
- The bond order for HF is 1 and for CO it is 3.
Molecular Orbitals Compatibility
- Not all combinations of atomic orbitals are feasible; molecular orbitals must maintain symmetries compatible with other molecules' symmetries.
- Symmetry adapted orbitals exist in two forms: in-phase and out-of-phase combinations.
Water Molecular Structure
- 2Px on oxygen does not interact with hydrogen orbitals and remains nonbonding due to cancelation of in-phase and out-of-phase overlaps.
- In-phase combinations of hydrogen atoms result in three molecular orbits (bonding, nonbonding, and anti-bonding).
- Out-of-phase combinations yield two molecular orbits (bonding and anti-bonding).
- Hydrogen fluoride (H2O) has lone pairs represented as a pure P orbital and an sp^n hybrid.
MO Theory Application
- Molecular orbital (MO) theory helps predict molecular structures by comparing calculated MO diagrams; the structure with the lowest energy is favored.
- Water exhibits a bent structure due to the interaction of the Pz orbital with the in-phase combination of hydrogen orbitals, providing additional stability not achievable in a linear configuration.
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Description
These flashcards cover the concepts of paramagnetism and diamagnetism as they relate to different molecular species. Test your knowledge by determining whether F2, O2, N2, C2, and B2 are paramagnetic or diamagnetic based on their molecular orbital diagrams. A great study aid for understanding molecular electronics and magnetic properties in chemistry.