Which of the following molecules is/are drawn showing correct 3D molecular geometry? Note that lone pairs have been omitted, but you should assume that octets are full. H H H H H 1 S-H _H H H H 2 1 2 HILCAH OTC-H エーロ H 3

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.

Indicate which of the following molecules are polar. Draw the molecular structure of each polar molecule, including the arrows that indicate the bond dipoles and the molecular dipole moment. (a) HCN (b) I2 (c) NO