CO 2 — nonpolar, dispersion forces only
CH 3 Cl — polar molecule
CH 3 OH — polar molecule, hydrogen bonds
NaCl — ionic compound

12. An imaginary metal crystallizes in a cubic lattice. The unit cell edge length is 100.

picometers (1 picometer = 1 × 10 –12meter). The density of this metal is 200. g/cm^3. The

atomic mass of the metal is 60.2 g/mol. How many of these metal atoms are there

within a unit cell?

A. 1.00

B. 2.00

C. 4.00

D. 6.00

E. 12.0

Answer: B

First, calculate the mass of one cell,100. pm on an edge:

..
./
g
1

200
1

100

10

1

1

100

200 10

cm m

cm

pm

m pm

3 g cell

3

12

(^33)
####= -^22
d n f p d n
Next, calculate the mass of one metal atom:
.
.
1 ../
60 2
602 10
1
mole 10 0 10 1 00 10
g
atoms
mole

23 23 22 g atom

==##--
Finally, calculate the number of metal atoms in one cell:
.
.
.
100 10
200 10
200
g atom
g cell
22 1 atoms/cell
22 1
#:
#:
--=

Liquids and Solids