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Chemistry LibreTexts

3.8.0.0: Bond Types and Molecular Orbital Theory (Problems)

  • Page ID
    210738
  • PROBLEM \(\PageIndex{1}\)

    How are the following similar, and how do they differ?

    (a) σ molecular orbitals and π molecular orbitals

    (b) bonding orbitals and antibonding orbitals

    Answer a

    Similarities: Both are bonding orbitals that can contain a maximum of two electrons. Differences: σ orbitals are end-to-end combinations of atomic orbitals, whereas π orbitals are formed by side-by-side overlap of orbitals

    Answer b

    Similarities: Both are orbitals that can contain two electrons. Differences: Bonding orbitals result in holding two or more atoms together. Antibonding orbitals have the effect of destabilizing any bonding that has occurred.

    PROBLEM \(\PageIndex{2}\)

    Can a molecule with an odd number of electrons ever be diamagnetic? Explain why or why not.

    Answer

    An odd number of electrons can never be paired, regardless of the arrangement of the molecular orbitals. It will always be paramagnetic.

    PROBLEM \(\PageIndex{3}\)

    Can a molecule with an even number of electrons ever be paramagnetic? Explain why or why not.

    Answer

    Yes, you could potentially have unpaired electrons in each orbital

    PROBLEM \(\PageIndex{4}\)

    Why are bonding molecular orbitals lower in energy than the parent atomic orbitals?

    Answer

    Bonding orbitals have electron density in close proximity to more than one nucleus. The interaction between the bonding positively charged nuclei and negatively charged electrons stabilizes the system.

    PROBLEM \(\PageIndex{5}\)

    Explain why an electron in the bonding molecular orbital in the H2 molecule has a lower energy than an electron in the 1s atomic orbital of either of the separated hydrogen atoms.

    Answer

    The pairing of the two bonding electrons lowers the energy of the system relative to the energy of the nonbonded electrons.

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