7.2 HW #18,19,20,41,42,43,44
18. Write the correct chemical formula for the compounds formed from each pair of ions.
+
2-
+
2-
a. K
, S
K
S
c. Na
, O
Na
O
2
2
2+
2-
3+
3-
b. Ca
, O
CaO
d. Al
, N
AlN
19. Write formulas for each compound.
a. barium chloride BaCl
c. lithium oxide Li
O
2
2
b. magnesium oxide MgO
d. calcium fluoride CaF
2
20. Which pairs of elements are likely to form ionic compounds?
a. Cl, Br
No
c. K, He
No
b. Li, Cl
Yes
d. I, Na
Yes
41. Which of the following pairs of atoms would you expect to combine chemically to
form an ionic compound?
a. Li and S Yes
d. F and Cl No
b. O and S No
e. I and K
Yes
c. Al and O Yes
f. H and N No
42. Identify the kinds of ions that form each ionic compound.
2+
-
a. calcium fluoride, CaF
Ca
F
2
3+
-
b. aluminum bromide, AlBr
Al
Br
3
+
2-
c. lithium oxide, Li
O
Li
O
2
3+
2-
d. aluminum sulfide, Al
S
Al
S
2
3
+
3-
e. potassium nitride, K
N
K
N
3
43. Explain why ionic compounds are electrically neutral.
Ionic compounds are electrically neutral because the positive charge of the cations is
balanced by the negative charge of the anions.
44. Which of the following pairs of elements will not form ionic compounds?
a. sulfur and oxygen – WILL NOT
c. sodium and sulfur – WILL
b. sodium and calcium – WILL NOT
d. oxygen and chlorine – WILL NOT