Chapter 1.9, Problem 29P

Indicate which molecules are polar and which are nonpolar. (a) SeO2 (b) N2O (N is the central atom) (c) SCl4

Formamide, HC(O)NH2, is prepared at high pressures from carbon monoxide and ammonia, and serves as an industrial solvent (the parentheses around the O indicate that it is bonded only to the carbon atom and that the carbon atom is also bonded to the H and the N atoms). Two resonance forms (one with formal charges) can be written for formamide. Write both resonance structures, and predict the bond angles about the carbon and nitrogen atoms for each resonance form. Are they the same? Describe how the experimental determination of the HNH bond angle could be used to indicate which resonance form is more important.

In each of the following molecules, a central atom is surrounded by a total of three atoms or unshared electron pairs: SnCl2, BCl3, SO2. In which of these molecules would you expect the bond angle to be less than 120? Explain your reasoning.

Best Lewis Formula and Molecular Geometry A student writes the Lewis electron-dot formula for the carbonate anion, CO32, 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.

• identify sigma and pi bonds in a molecule and explain the difference between them.

For each of the following molecules, state the bond angle (or bond angles, as appropriate) that you would expect to see on the central atom based on the simple VSEPR model. Would you expect the actual bond angles to be greater or less than this? a CCl4 b SCl2 c COCl2 d AsH3

Ketene, C2H2O, is a reactant for synthesizing cellulose acetate, which is used to make films, fibers, and fashionable clothing. (a) Write the Lewis structure of ketene. Ketene does not contain an OH bond. (b) Identify the electron-region geometry and the molecular geometry around each carbon atom and all the bond angles in the molecule. (c) Identify the hybridization of each carbon and oxygen atom. (d) Is the molecule polar or nonpolar? Use appropriate data to support your answer.

Consider the following compounds: CO2, SO2, KrF2, SO3, NF3, IF3, CF4, SF4, XeF4, PF5, TF5, and SCl6. These 12 compounds are all examples of different molecular structures. Draw the Lewis structures for each and predict the molecular structures. Predict the bond angles and the polarity of each. (A polar molecule has a net dipole moment, while a nonpolar molecule does not.) See Exercises 25 and 26 for the molecular structures based on the trigonal bipyramid and the octahedral geometries.

Two compounds have the molecular formula N3H3. One of the compounds, triazene, contains an NN bond; the other compound, triaziridene, does not. (a) Write the correct Lewis structures for each compound. (b) Approximate the bond angle between the three nitrogen atoms in each compound.