7)
a. Solid K has an electron configuration of [Ar]4s1, so it has an unpaired electron. This allows electric current to flow through the structure. KNO3 does not have an unpaired electron, so no electricity flow in.
b. SbCl3 has measurable dipole movement because the molecule is polar, so there is attraction between SbCl3 and other polar molecules. SbCl5 is non-polar, so there is no dipole interaction occurring.

isn't chemistry fun!

c. Both of these molecules are non-polar, but CBr4 has the higher boiling point because it has more electrons, and therefore it is harder to separate.
d. NaI is polar, so it is easy for it to bond with other molecules in a solution. I2 is non-polar and symmetrical, so it is harder to separate.
f. Sulfur has an expanded octet (12 electrons) because it is in the third energy level, so there are more options for bonding. Oxygen is only in the second energy level, and therefore is restricted to 8 electrons.