CHEM 112 Lecture Notes - Lecture 21: Sigma Bond, Antibonding Molecular Orbital, Electron Configuration

50 views2 pages

amethystbee103

14 Nov 2018

School

Department

Course

Professor

For unlimited access to Class Notes, a Class+ subscription is required.

Document Summary

Where there are antibonding ones it means that there are nodes there. This is a force that is repelling the electrons beside each other. At the node there is no electron density. Each mo can be represented mathematically as a linear combination of aos. The total number of mos is equal to the total number of aos. Mos can be classified as bonding, antibonding, or nonbonding. The electron configuration for the molecule is obtained by placing electrons into the mos according to their energies (from low to high) following similar hund"s rules. Stable species have more electrons in bonding mos than antibonding mos. Bond order= # of electrons in the bonding mos -# of electrons in antibonding mos/2. Bond order is defined as how many bonds are holding these nuclei together. For example b. o for h2= (2-0)/2=1 (so single bond) B. o for he2=(2-2)/2=0 there is no bond between these two nuclei so there is an unstable molecule.

Related Questions

The molecular orbitals associated with the Ï-bonding MOs insquare cyclobutadiene (C4H4) are, like benzene, form by overlap ofa single p-orbital on each carbon atom that is not involved in thesigma-bonding network of the molecule. These p-orbitals pointperpendicularly with respect to the plane defined by the carbonatoms. There is no central atom, so the only interactions thatmatter are between the p-orbitals among themselves. These MOs haveexactly the same phase relationship as the SALCs you just made inquestion 1. i) Use your results from question 1 to draw the fourÏ-orbitals of C4H4. ii) Use the idea that the energy of a MOincreases with number of new nodes made during bonding (i.e. nodesnot already present in initial AO functions) to sketch a molecularorbital energy level diagram for the Ï-molecular orbitals of C4H4.Remember that, by definition, degenerate orbitals are identicalexcept for trivial rotation in space, and have identical energy.iii) Fill the MOs with the electrons from the atomic p-orbitalsthat you used to form the Ï-MOs of C4H4. Use your diagram todetermine the overall bond order by considering each doublyoccupied bonding MO to contribute 1, each nonbonding orbital 0 andeach antibonding orbital -1. The result would be divided by 4 C-Cbonds to get the average contribution to each C-C bond fromÏ-bonding, which then should be added to a Ï-bonding contributionof 1.0. iv) Repeat step (iii) for the dication C4H4 2+ to determinethe net bond order for this species. Why do you think you got thisvalue? v) Predict which of C4H4 and C4H4 2+ could be observed byESR spectroscopy. vi) Which of C4H4 2+ and C4H4 is more likely tobe susceptible to electrophilic attack.

CHEM 112 Lecture Notes - Lecture 21: Sigma Bond, Antibonding Molecular Orbital, Electron Configuration

Document Summary

Get access

Related textbook solutions

Chemistry: Structure and Properties

Basic Chemistry

Principles of Chemistry Molecular Approach

Principles of Chemistry Molecular Approach

Chemistry: Structure and Properties

Chemistry: A Molecular Approach

Chemistry: A Molecular Approach

Principles of Chemistry: A Molecular Approach

Chemistry: The Central Science

Related Documents

CHEM 112 Chapter Notes - Chapter 11.5 and 11.2: Molecular Orbital Theory, Pauli Exclusion Principle, Atomic Orbital

CHEM 112 Chapter Notes - Chapter 8.7-8.12 and 9.1=9.7: Unpaired Electron, Pauli Exclusion Principle, Electron Configuration

Chemistry 1027A/B Chapter Notes - Chapter 2.4: Molecular Orbital Diagram, Molecular Orbital Theory, Antibonding Molecular Orbital

Related Questions