Chemistry 121 - Quiz 4

Five chemically relevant hybridization combinations of orbitals:

sp, sp², sp³, sp³d, sp³d²

Linear

- 2 - 180° - sp

Trigonal Planar

- 3 - 120° - sp²

Tetrahedral

- 4 - 109.5° - sp³

Trigonal Bipyramidal

- 5 - 120° and 90° - sp³d

Octahedral

- 6 - 90° - sp³d²

To determine the hybridization scheme for a covalently bonded atom:

1. Draw the Lewis structure for the molecule. 2. Determine the parent shape using VSEPR theory. 3. Match the parent shape to the appropriate hybridization scheme.

Bond Order Equation

BO = (B - AB)/2

Estimate of Length

Double Bond: 1.35A Single Bond: 1.54A Carbon Radius:0.77A

What does HOMO and LUMO stand for?

HOMO: highest occupied molecular orbital (single e⁻). LUMO: lowest unoccupied molecular orbital (no e⁻).

MO Energy Levels Decrease from...

Left to Right

Paramagnetic Diamagnetic

Paramagnetic: contains unpaired electrons. Diamagnetic: all electrons are paired.

1. Complete the orbital interaction diagram for dioxygen below by adding the appropriate number of electrons. What feature of the diagram agrees with the prediction that dioxygen is paramagnetic? Assume that the O₂ molecule is oriented along the x-axis. 2. What is the bond order of O₂? 3. a) What is the name of the HOMO in O₂? b) What is the name of the LUMO in O₂?

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Consider elemental oxygen, O₂, where the nuclei both lie on the z-axis (the choice of internuclear axis is arbitrary, and in the previous example, we used the x-axis). a) Which orbitals can overlap to form the O-O (sigma)-bond? b) Which orbitals can overlap to form the O-O (pi)-bond? c) Sketch cross-sections for the (sigma) and (pi) bonds in oxygen.

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For each of the following ions, i) draw an orbital interaction diagram, ii) calculate the bond order, iii) write the molecular orbital electronic configuration, and iv) classify the species as paramagnetic or diamagnetic. [N₂]²⁻

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Use valence bond theory to predict whether He₂ can be formed.

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Orbital Configuration

Shown by arrows in each orbit with direction indicating spin.

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antibonding bonding