Answers to book problems
Page 177
1. Ionic bonding involves losing and gaining electrons to form ions and involves the attraction between large
numbers of + and – ions. There are no individual molecules in ionic compounds. Covalent bonding involves
sharing electron pairs between atoms.
2. A large difference in electronegativity between two atoms causes the bonding to be ionic. A small difference in
electronegativity between two atoms causes the bonding to be covalent (molecular).
3. A. ionic
b. polar-covalent
c. polar-covalent
4. I and Br, Cu and S, Li and F
5.
a. Cu Cl has the greater % ionic character because it has the greater difference in electronegativity
b. The chlorine in CuCl has the greater negative partial charge compared to the chlorine in ICl because
there is a greater difference in electronegativity, so the electrons in the CuCl bond get pulled more
toward the Cl in CuCl than they do toward the Cl in ICl
Page 209
3. The greater the electronegativity difference between two atoms is, the more ionic the bond between them is.
4. a. Polar refers to bonds that have an uneven distribution of charge. In other words, the shared electrons in the bond
are attracted more to one side than the other.
b. In a polar-covalent bond the electron pair is not shared equally by the two bonded atoms. (The electrons are closer to
one atom than the other.) In a nonpolar-covalent bond, the electron pair is shared equally between the two bonded
atoms.
5. Atoms form chemical bonds if it lowers their potential energy. In other words, they bond if it makes them more
stable.
6.
Electronegativity
(from page 161)
H 2.1
S 2.5
K 0.8
Si 1.8
K 0.8
Se 2.4
C 2.5
Electronegativity
(from page 161)
I 2.5
O 3.5
Br 2.8
Cl 3.0
Cl 3.0
S 2.5
H 2.1
Difference
0.4
1.0
2.0
1.2
2.2
0.1
0.4
Probable Bond Type
(see page 176)
Polar-covalent
Polar-covalent
ionic
Polar covalent
ionic
Nonpolar-covalent
Polar-covalent
7. The pairs above listed from most ionic to most covalent:
K and Cl, K and Br, Si and Cl, S and O, tie between H and I and C and H, Se and S
Which atom is more
electronegative?
I
O
Br
Cl
Cl
S
C
Page 194, #4. B is molecular, A is ionic. The intermolecular attractions that hold molecules together are weaker than
the attraction between ions in an ionic compound. This causes lower melting and boiling points in molecular
substances.