Lewis formula and molecular geometry

Question

Assignment:

Concept Explorations

Best Lewis Formula and Molecular Geometry

A student writes the Lewis electron-dot formula for the carbonate anion, CO₃^2-, as

a. Does this Lewis formula obey the octet rule? Explain. What are the formal charges on the atoms? Try describing the bonding for this formula in valence bond terms. Do you have any difficulty doing this?

b. Does this Lewis formula give a reasonable description of the electron structure, or is there a better one? If there is a better Lewis formula, write it down and explain why it is better.

c. The same student writes the following resonance description for CO₂: Is there something wrong with this description? (What would you predict as the geometries of these formulas?)

d. Is one or the other formula a better description? Could a value for the dipole moment help you decide?

e. Can you write a Lewis formula that gives an even better description of CO₂? Explain your answer.

Molecular Geometry and Bonding

Draw four different Lewis electron-dot formulas for the SeO₂ molecule. (HINT: One should have two single bonds, two have a single and a double bond, and one two double bonds).

a. Are there any electron-dot formulas that you expect to give the best description? How would you describe the bonding in terms of electron-dot formulas?

b. Describe the bonding in SeO₂ in valence bond terms. If there is delocalized bonding, note this in your description and explain how molecular orbital theory can be useful here.

c. Determine the arrangement of electron pairs about Se in the SeO₂ molecule. What would you expect for the molecular geometry of the SeO₂ molecule?

d. Would you expect the O-Se-O angle in the SeO₂ molecule to be greater than, equal to, or less than 120°. Explain your answer.

e. Draw an electron-dot formula for the H₂Se molecule and determine its molecular geometry.

f. Compare the H-Se-H bond angle to the O-Se-O bond angle. Is it larger or smaller? Explain.

g. Determine whether the H₂Se and SeO₂ molecules have dipole moments. Describe how you arrived at your answer.

Provide complete and step by step solution for the question and show calculations and use formulas.