Answer Key
Chapter 7
Practice Problems
1. neutral Br: 1s22s22p63s23p64s23d104p5; ion: Br, anion,
1s22s22p63s23p64s23d104p6
2. neutral Ga: 1s22s22p63s23p64s23d104p1; ion: Ga3, cation,
1s22s22p63s23p63d10
3. neutral S: 1s22s22p63s23p4; ion: S2, anion, 1s22s22p63s23p6
4. neutral Rb: 1s22s22p63s23p64s23d104p65s1; ion: Rb, cation,
1s22s22p63s23p64s23d104p6
5. Al: [Ne]3s2 3p1; F: [He]2s2 2p5; one Al for every three F
6. Li: [He]2s1; O: [He]2s22p4; two Li for every O
7. Be: [He]2s2; Se: [Ar]4s23d104p4; one Be for every Se
8. Ga: [Ar]4s23d104p1; S: [Ne]3s23p4; two Ga for every three S
9. a. not ionic
10.
11.
12.
13.
14.
15.
16.
17.
18.
27.
b. not ionic
c. ionic
d. ionic
a. LiF
b. MgS
c. MgO
Na2S
19. Ca(OH)2
Mg3N2
20. ammonium iodide
K3P
21. sodium bromate
BaF2
22. magnesium nitrate
AlN
23. potassium hydrogen sulfate
Na3PO4
24. ammonium perchlorate
(NH4)2CO3
25. aluminum hypochlorite
Al2(CrO4)3
26. iron(II) fluoride
not conclusively, because ionic solids also conduct electricity when
melted
28. malleability; no, because metals are malleable
Answer Key (continued)
29. nickel, because nickel is a metal and metals are good conductors of
electricity; ductility, malleability, metallic luster, very high boiling
point
30. an interstitial alloy
31. a substitutional alloy
Chapter 7 Review
32. A chemical bond is a force that holds two atoms together. Elements
tend to form bonds so as to achieve the stable electron configuration
of a noble gas.
33. A cation is a positively charged ion formed when one or more
electrons are transferred from an atom. An anion is a negatively
charged ion formed when one or more electrons are transferred to
an atom. An example of a cation is the sodium ion, Na. An
example of an anion is the chloride ion, Cl.
34. An ionic bond is the electrostatic force that holds oppositely
charged ions together in an ionic compound. A potassium atom
transfers its valence electron to an iodine atom, resulting in a
potassium cation and an iodide anion, which form an ionic bond
because of their opposite charges.
35. Ionic compounds are made up of a three-dimensional crystal lattice,
with positive ions surrounded by negative ions, and vice versa.
Typical properties include high melting and boiling points,
brittleness, inability to conduct electricity when solid, and ability to
conduct electricity when melted or dissolved in water.
36. Determine the charge of each type of ion, generally by referring to
the periodic table or a table of common ions. Then choose numbers
of positive and negative ions such that the sum of the positive and
negative charges is zero. Write the symbols for the atoms and use
subscripts to show the number of each ion per formula unit.
Answer Key (continued)
37. If there are two oxyanions, the one with fewer oxygen atoms per ion
is named using the suffix -ite. The name of the oxyanion with more
oxygen atoms has the suffix -ate. In the case of the halogens, if
there is one oxygen atom, use the prefix hypo- and the suffix -ite. If
there are two oxygens, use the suffix -ite. If three, use the suffix ate. If four, use the prefix per- and the suffix -ate.
38. The valence electrons are delocalized, forming a mobile sea of
electrons that attract the metallic cations. The mobility of the
electrons accounts for malleability and ductility, which require
the particles to move past each other, and for the ability to conduct
electricity, which requires electrons to flow easily. The delocalized
electrons also interact with light, which accounts for metallic luster.
Boiling points tend to be extremely high because of the difficulty of
completely removing atoms from the attracting electrons and
cations. Melting points are considerably lower because of the ability
of the particles to move past each other.
39. Both are mixtures that have metallic properties. In substitutional
alloys, atoms of the original metal have been replaced by other
metal atoms of similar size. In interstitial alloys, small holes in a
metallic crystal have been filled with smaller atoms.