3.8.0.0: Bond Types and Molecular Orbital Theory (Problems)

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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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Contributors and Attributions

Paul Flowers (University of North Carolina - Pembroke), Klaus Theopold (University of Delaware) and Richard Langley (Stephen F. Austin State University) with contributing authors. Textbook content produced by OpenStax College is licensed under a Creative Commons Attribution License 4.0 license. Download for free at http://cnx.org/contents/85abf193-2bd...a7ac8df6@9.110).
Adelaide Clark, Oregon Institute of Technology

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