pathways for a variety of scientists and technicians. The development, maintenance, and
applications of the equipment for future science discovery not only will help us develop
cleaner technologies for future use, but also will allow us to deal with some of the messes
left behind by older technologies. As we move forward, new technologies will lead to
new discoveries and new discoveries will lead to new technologies.
Section 3.1 Review Answers
(Student textbook page 109)
Checking Concepts
1. Chlorine has toxic properties that make it useful as a disinfectant but a hazard to
human health if used improperly.
2. HHPS stands for Hazardous Household Product Symbols. The upside-down triangle
means that the container is dangerous. The octagon means that the contents of the
container are dangerous. The explosion symbol means the container may explode.
The symbol showing bones in a hand immersed in liquid means the product can
burn human tissue. The flame symbol means the product or its fumes will catch fire
easily. The skull and crossbones symbol means the product is poisonous.
3. Chemists classify compounds as ionic or molecular. Ionic compounds are made
of ions and molecular compounds are made of molecules. These compounds have
characteristic properties. For example, ionic compounds conduct electric current
when dissolved in water while molecular compounds do not.
4. An atom is electrically neutral. An ion is a charged atom or group of atoms.
5. Ice cream, hand sanitizer, a plastic bottle, air, and paper all contain chemical
compounds.
6. Sample answer:
Properties of Ionic and Molecular Compounds
Ionic Compounds
Molecular Compounds
melting and boiling
points
high
low, in general
ability to conduct
electric current
conduct electric current in liquid or
when dissolved, not as solid
do not conduct
hardness or softness
tend to be hard and brittle and
break along straight lines
solids tend to be soft
7. The covalent bonds in molecular compounds and the ionic bonds in ionic
compounds are very strong. However, covalent bonds are formed when atoms
share electrons and ionic bonds are formed when atoms transfer electrons, creating
oppositely charged ions that are then attracted to one another.
8. Ionic compounds are neutral because the positive charges and negative charges of
the ions are perfectly balanced.
9. The 3
3 means that atoms of the element tend to form ions with charges of 3
3 in
ionic compounds.
Understanding Key Ideas
10. The term “lattice structure” describes the regular, repeating pattern in which ions,
such as sodium and chloride ions, are arranged in an ionic compound such as
sodium chloride.
11. For electric current to be conducted, there must be a source of mobile charges. In
solid calcium chloride, the calcium ions and chloride ions are held tightly in a lattice
TR-2-28 MHR • Unit 2 Chemical Reactions 978-0071058117
Answers to Check Your Understanding Questions
(Student textbook page 113)
7. Atoms of elements in Group 17 form ions with a charge of 1.
1 . Atoms
A
of elements in
Group 16 form ions with a charge of 2.
2 . Atoms
A
of elements in Group 15 form ions
with a charge of 3.
3 .
8. (a) Binary; it consists of two elements only
(b) Binary; it consists of two elements only
(c) Not binary; it consists of three elements
(d) Not binary; it consists of three elements
9. (a) rubidium bromide
(b) magnesium oxide
(c) strontium fluoride
10. (a) potassium bromide
(b) magnesium chloride
(c) magnesium selenide
(d) sodium sulfide
(e) lithium nitride
(f) aluminum bromide
(g) beryllium fluoride
(h) rubidium bromide
Answers to Practice Problems
(Student textbook page 115)
1. (a) NaBr
(b) K2S
(c) ZnI2
(d) Mg3N2
2. (a) NaI
(b) ZnO
(c) MgCl2
(d) K2Se
(e) Ag2S
(f) AlI3
(g) AlP
(h) CaO
(i) CaS
(j) RbBr
3. The chemical formula of silver iodide is AgI.
Answer to Caption Question
Figure 3.14 (Student textbook page 116): The colour difference of the two samples
indicates that they are two different compounds with different properties.
Answers to Check Your Understanding Questions
(Student textbook page 117)
11. (a) vanadium(IV)
978-0071058117
Chapter 3 Chemical Names, Formulas, and Equations • MHR TR-2-33
(b) nickel(III)
(c) gold(I)
(d) titanium(IV)
12. (a) NiCl3
(b) PbS2
(c) Cu2O
(d) CuO
Answers to Practice Problems
(Student textbook page 117)
4. (a) cobalt(III) oxide
(b) manganese(IV) sulfide
(c) copper(II) chloride
(d) copper(I) chloride
5. (a) iron(II) oxide
(b) copper(I) nitride
(c) tin(IV) sulfide
(d) tin(II) nitride
(e) nickel(III) sulfide
(f) nickel(II) sulfide
(g) lead(IV) fluoride
(h) titanium(IV) sulfide
Answer to Caption Question
Figure 3.17 (Student textbook page 118): Shellfish get calcium ions and carbonate ions
from the amino acids in the organisms they eat and from dissolved salts in seawater.
Answers to Practice Problems
(Student textbook page 119)
6. (a) Ba(NO3)2
(b) K2CO3
(c) NiSO4
(d) Mg3(PO4)2
(e) Na2Cr2O7
(f) FeCrO4
(g) Pb(CH3COO)4
(h) (NH4)2SO4
7. (a) The formula shows phosphide, not phosphate as the negative ion. The correct
formula is Na3PO4.
(b) The formula is missing parentheses around the nitrate ion. The correct formula
is Mg(NO3)2.
(c) The formula is missing the subscript “2” for the potassium ion. The correct
formula is K2SO3.
(d) The formula has unnecessary parentheses around the hydroxide ion. The correct
formula is NaOH.
8. CaSO4
TR-2-34 MHR • Unit 2 Chemical Reactions 978-0071058117
5. For an ionic compound, the chemical formula represents the ratio of the ions in the
compound. The ratio 3:6 can be further reduced to 1:2 so the formula should be
written as CaF2.
6. Of the compounds given, the following are binary compounds: AlCl3, H2O, MgS,
and PbF2.
7. (a) silver chloride, AgCl
(b) zinc oxide, ZnO
(c) beryllium iodide, BeI2
(d) magnesium fluoride, MgF2
8. (a) 4
4
(b) 2
2
(c) 3
3
(d) 3
3
9. You need to know which ion of iron is part of the oxide. You would probably be
given this information through the name of the iron ion, that is, iron(II) or iron(III).
10. Mercury could form mercury(I) oxide, HgO2, or mercury(II) oxide, HgO.
Understanding Key Ideas
11. Both sodium and magnesium atoms tend to lose electrons to atoms of other
elements and form positive ions when they form ionic compounds.
12. “Electron accounting” is a helpful way to think of writing formulas for ionic
compounds because you need to ensure that the final formula represents a neutral
compound. You need to keep track of the electrons “lost” by the positive ions and
the electrons “gained” by the negative ions. The ions are present in such a ratio that
the “lost” column equals the “gained” column, just as in accounting.
13. The name copper(II) chloride is correct. The ionic compound that contains a ratio
of 1 copper ion to 2 chloride ions must contain the copper(II) ion for the charges to
balance.
14. (a) Fe3N2
(b) PbO
(c) Cu2S
(d) SnF4
15. (a) NO2
(b) SO3
(c) N2O4
(d) PCl5
16. (a) aluminum phosphate
(b) sodium carbonate
(c) potassium hydrogen carbonate
(d) magnesium hydroxide
17. (a) Na2SO4
(b) Mg3(PO4)2
(c) Ca(NO3)2
(d) Al(ClO2)3
18. (a) CuClO3
(b) Fe3(PO4)2
TR-2-40 MHR • Unit 2 Chemical Reactions 978-0071058117
(c) Sn(CO3)2
(d) Ni(MnO4)2
Project Prep
Sample answer: Using systematic names and formulas in the planning and analysis of
a scientific investigation is vitally important because in the absence of agreed-upon
nomenclature and formula-writing conventions, scientists could not communicate their
results clearly and unambiguously to their peers in the global scientific community.
Acceptable student answers will reflect this key advantage of using systematic names and
formulas.
978-0071058117
Chapter 3 Chemical Names, Formulas, and Equations • MHR TR-2-41