Chapter 5

Use Lewis structures to explain why Br3- and I3- are stable, while F3- is not.

Draw the Lewis structure for HCSNH2. (The carbon and nitrogen atoms are bonded together, and the sulfur atom is bonded to the carbon atom.) Label each bond in the molecule as polar or nonpolar.

Draw the Lewis structure for urea, H2NCONH2, one of the compounds responsible for the smell of urine. (The central carbon atom is bonded to both nitrogen atoms and to the oxygen atom.) Does urea contain polar bonds? Which bond in urea is most polar?

The azide ion, N3-, is a symmetrical ion, and all of its contributing resonance structures have formal charges. Draw three important contributing structures for this ion.

One form of phosphorus exists as P4 molecules. Each P4 molecule has four equivalent P atoms, no double or triple bonds, and no expanded octets. Draw the Lewis structure for P4.

Draw the Lewis structure for acetamide (CH3CONH2), an organic compound, and determine the geometry about each interior atom. Experiments show that the geometry about the nitrogen atom in acetamide is nearly planar. Which resonance structure can account for the planar geometry about the nitrogen atom?

In the very first chapter of this book, we described the scientific approach and put a special emphasis on scientific models or theories. In this chapter, we looked carefully at the Lewis model of chemical bonding. Why is this theory successful? What are some of the limitations of the theory?

Draw the Lewis symbols for the atoms Al and O. Use the Lewis model to determine the formula for the compound that forms from these two atoms.

Draft a list of step-by-step instructions for writing the correct Lewis structure for any molecule or polyatomic ion.

Pass a piece of paper around the group and ask each group member in turn to perform the next step in the process of determining a correct Lewis structure (including formal charges on all atoms and resonance structures, if appropriate) for the following molecules and ions: N2H4, CCl4, CO3 2-, and NH4+.

In complete sentences, describe why someone might expect the bond angles in methane (CH4) to be 90 degrees, although the bonds are actually 109.5 degrees.

At least two different numbers of electron groups can result in a linear molecule. What are they? What are the numbers of bonding groups and lone pairs in each case? Provide an example of a linear molecule in each case.