Cliffs AP Chemistry, 3rd Edition

(d) PCl 3 has a dipole; PCl 5 does not.

• PCl 3 Lewis diagram:


• PCl 3 — note the lone pair of unshared electrons.


• PCl 3 is pyramidal, and all pyramidal structures are polar.


• PCl 5 Lewis diagram:


• PCl 5 — no unshared electrons on P


• PCl 5 is trigonal bipyramidal and thus perfectly symmetrical, so there is no polarity;
  all dipoles cancel.

2. Solids can be classified into four categories: ionic, metallic, covalent network, and
   molecular. For each of the four categories, identify the basic structural unit; describe the
   nature of the force both within the unit and between units; cite the basic properties of
   each type of solid; give two examples of each type of solid; and describe a laboratory
   means of identifying each type of solid.

Answer

This question lends itself to the chart format. Here the column headings express what is given,
and the first entry in each row serves as a restatement of what is wanted.

Characteristic Ionic Metallic Covalent Network Molecular

Structural Unit ions cations atoms polar or nonpolar

surrounded by molecules

mobile “sea”

of electrons

Force Within Unit covalent bond covalent bond

(Intra) within polyatomic

ion

(continued)

P

Cl

Cl

Cl

Cl

Cl

P

Cl

Cl

Cl

Liquids and Solids