Assistant with Chemistry Homework sheets

Naming Ionic CompoundsWhat are the structural units that make up ionic compounds and how are they named?
Why?
When working in chemistry, it is often convenient to write a chemical in symbols. For example we might
write down the substance table salt as NaCl. In talking about chemistry however, it is a bit tacky to say
“en-ay see-ell” when we want to refer to a substance. Also, in formal writing we should use the name of
the compound rather than its symbols. Therefore we need to learn how to say the proper names of ionic
substances.
Model 1 – Ion Charges for Selected Elements
1
H+
2
Li+
Be2+
3
Na+
Mg2+
4
K+
Ca2+
5
Rb+
Sr2+
6
Transition elements
Fe2+
Fe3+
Ba2+
Ni2+
Ni3+
Cu+
Cu2+
Al3+
N3–
O2–
F1–
P3–
S2–
Cl1–
Zn2+
Ag1+
Hg22+
Hg2+
Br1–
Sn2+
Sn4+
Pb2+
Pb4+
Cations
1. Based on the information in Model 1:
a. Identify three elements that form only one cation.
I1–
Anions
b. Identify three elements that form only one anion.
c. Identify three elements that form more than one cation.
d. In what region of the periodic table are these “multiple ion” elements usually located?
2. Consider the ions of potassium (K) and sulfur (S). Write chemical formulas for all possible ionic
compounds involving these ions, using the simplest ratio(s) of potassium (K) and sulfur (S).
Keep in mind that the sum of the charges in an ionic compound must equal zero.
3. Consider the ions of iron (Fe) and sulfur (S). Write chemical formulas for all possible ionic compounds involving these ions, using the simplest ratio(s) of iron (Fe) and sulfur (S). Keep in mind
that the sum of the charges in an ionic compound must equal zero.
Naming Ionic Compounds
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Model 2 – Ionic Compound Names (Metals that form one ion)
NaCl Sodium chloride
Zn3P2 Zinc phosphide
CaS
Al2O3 Aluminum oxide
Calcium sulfide
Ag2S Silver sulfide
SrCl3 Strontium chloride
4. Circle the symbol for the metal in each of the compounds in Model 2.
5. Which element comes first in the name and formula of the compounds in Model 2—the metal
or the nonmetal?
6. Use the table of ions in Model 1 to answer the following questions:
a. In the compound zinc phosphide, what is the charge on the zinc ion?
b. In the compound zinc phosphide, what is the charge on the phosphide ion?
7. Explain why a 3 to 2 ratio of ions is necessary for the compound zinc phosphide.
8. The compound carbon dioxide has a name that gives you a hint as to how many oxygen atoms
are in the compound. Is there anything in the name “zinc phosphide” that indicates there are
three zinc and two phosphorus ions in the formula unit?
9. Is there any other ratio of zinc and phosphorus ions that could exist? For instance, could you
have Zn2P or ZnP2? Explain your answer.
10. Explain why you don’t need to specify the number of ions in the compound when you are naming ionic substances like those in Model 2.
11. Model 2 is labeled “Metals that form one ion.” What other metals that also form only one ion
could be included in the Model 2 list? Model 1 may be helpful in this regard.
12. Describe how the names of the nonmetal elements in Model 2 are changed when they are in
their anion forms.
13. Name the following ionic compounds using what you learned from Model 2.
Li2O
2
MgF2
Al2S3
K3N
POGIL™ Activities for High School Chemistry
14. Provide the chemical formula for each of the following ionic compounds.
Barium chloride
Magnesium oxide
15. Consider the two chemical formulas you wrote in Question 3 for compounds of iron and sulfur.
Would the name “iron sulfide” be sufficient to uniquely identify either of those compounds?
Explain.
Read This!
When the metal in an ionic compound always forms an ion with the same charge, you need not indicate
that charge as part of the compound name. However, some atoms have the ability to form more than one
type of ion. This can make naming confusing. You can’t simply refer to a compound of copper and oxygen
as “copper oxide.” People won’t know which compound you are referring to—CuO or Cu2O.
Model 3 – Ionic Compound Names (Metals that form multiple ions)
Cu2O Copper(I) oxide
PbO Lead(II) oxide
CuO Copper(II) oxide
PbO2 Lead(IV) oxide
SnF2
Tin(II) fluoride
FeCl2 Iron(II) chloride
SnF4
Tin(IV) fluoride
FeCl3 Iron(III) chloride
16. Model 3 is labeled “Metals that form multiple ions.” What other metals that form multiple ions
could be included in Model 3? Model 1 may be helpful in this regard.
17. Describe the most obvious difference between the names in Model 3 and those in Model 2.
18. Do the Roman numerals in the names in Model 3 relate to the number of cations or number of
anions in the formula unit? Support your answer by citing two specific examples.
19. Keeping in mind that the sum of the charges in an ionic compound must equal zero, use the
chemical formulas in Model 3 to answer the following questions:
a. Identify the charge on the copper cations in copper(I) oxide and copper(II) oxide, respectively.
b. Identify the charge on the iron cations in iron(II) chloride and iron(III) chloride, respectively.
20. What do the Roman numerals in the compounds described in Question 19 indicate?
Naming Ionic Compounds
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21. Fill in the table below using what you’ve learned from Model 3.
Compound
PbCl4
Fe2O3
SnO
CuBr2
Charge on Cation
Pb4+
Name of the Compound
Lead(IV) chloride
22. For each of the compounds in the table below, determine the type of metal in the compound and
then name the compound using the correct naming method.
Metal forms
only one ion
Metal forms
multiple ions
Name
CaBr2
MgO
Ag3N
SnCl2
CuF2
K3P
Zn3N2
HgO
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POGIL™ Activities for High School Chemistry
Extension Questions
Model 4 – Traditional Names for Ionic Compounds
Metals that form one ion
Metals that form multiple ions
NaCl Sodium chloride
Cu2O Cuprous oxide
CaS
CuO Cupric oxide
Calcium sulfide
Ag2S Silver sulfide
SnF2
Stannous fluoride
Zn3P2 Zinc phosphide
SnF4
Stannic fluoride
23. Look at the traditional names in Model 4 for ionic compounds containing metals that form
only one ion. What are the similarities and differences between the traditional naming system in
Model 4 and the stock naming system in Model 2 for these kinds of ionic compounds?
24. Look at the traditional names in Model 4 for ionic compounds containing metals that form
multiple ions. What are the similarities and differences between the traditional naming system in
Model 4 and the stock naming system in Model 3 for these kinds of ionic compounds?
25. Do the “-ous” and “-ic” endings in the compound names in Model 4 refer to a particular metal
ion charge? Explain.
26. Examine the traditional ion names shown below for selected metals. Write a rule for using the
“-ous” and “-ic” endings for metal ions.
Cu2+ cupric
Fe3+ ferric
Sn4+ stannic
Pb4+ plumbic
Cu1+ cuprous
Fe2+ ferrous
Sn2+ stannous
Pb2+ plumbous
27. Complete the table and write the traditional name for each ionic compound.
Metal forms
only one ion
Metal forms
multiple ions
Name
CaBr2
MgO
Ag3N
SnCl2
CuF2
K3P
Zn3N2
HgO
Naming Ionic Compounds
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28. Write the chemical formula for each ionic compound below.
aluminum bromide
stannic sulfide
iron(II) chloride
lithium oxide
plumbous oxide
29. Throughout this activity you have developed a process for naming an ionic compound when
given a formula. On a separate sheet of paper, create a flowchart of questions that you might ask
yourself when naming an ionic compound.
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POGIL™ Activities for High School Chemistry
Polyatomic Ions
Can a group of atoms have a charge?
Why?
Do you know you eat a lot of “-ates”? Next time you look at a food label, read the ingredients and you will
likely find a number of ingredients that end with “-ate,” such as sodium phosphate or calcium carbonate.
Did you ever wonder what the chemical formulas of these ingredients look like? In this activity we will
explore polyatomic ions, which are groups of atoms that carry a charge. These ions are found in our food
ingredients, natural waterways, and many other chemical compounds you encounter every day.
Model 1 – Types of Ions
Nitride
Monatomic
Ions
N
Sulfide
3–
O
O
H
2–
S O
O
1+
N H
H
H
Sulfite
Nitrite
1–
Ammonium
O
1–
O
Hydroxide
1–
O
Cl
Sulfate
N
Polyatomic
Ions
2–
S
Nitrate
O
Chloride
2–
O
O
N
S
O
O
1–
O
H
1. Use Model 1 to complete the table below.
Name of Ion
Charge on Ion
Type and
Number of
Atoms
Chemical
Formula
Polyatomic Ions
Nitride
Nitrate
Sulfate
Sulfite
Ammonium
-1
1 sulfur
4 oxygen
SO32–
1
2. Consider the terms “monatomic” and “polyatomic” as they are used in Model 1. Write a definition for each of these terms. It may be helpful to break the words apart (i.e., poly – atomic).
Make sure your group comes to consensus.
Monatomic—
Polyatomic—
3. What types of elements (metals or nonmetals) are shown in the polyatomic ions in Model 1?
4. What type of bonds (ionic or covalent) hold the atoms together in polyatomic ions? Explain your
reasoning.
5. The net charge on a sulfide ion (S2–) is –2. Explain how this ion obtains its charge. Your answer
should include a discussion of subatomic particles.
6. The dotted line around each polyatomic ion in Model 1 shows that the group of atoms has a
charge. The charge is not on any one atom, but rather on the group of atoms as a whole.
Based on your knowledge of monatomic ions, propose an explanation for the net charge on a
polyatomic ion. Your answer should include a discussion of subatomic particles.
7. What are the similarities and differences between the nitrate and nitrite ions in Model 1?
8. What are the similarities and differences between the sulfate and sulfite ions in Model 1?
9. The “chlorate” polyatomic ion has a charge of –1 and is composed of one chlorine atom (the
central atom) and three oxygen atoms.
a. Draw a model of a chlorate ion.
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POGIL™ Activities for High School Chemistry
b. Write the chemical formula for the chlorate ion, including its charge.
10. In your group discuss what “chlorite” would look like.
a. Draw a model of a chlorite ion.
b. Write the chemical formula for the chlorite ion, including its charge.
Model 2 – Common Polyatomic Ions
1+
ammonium
NH4
1+
1–
acetate
CH3COO1–
hydroxide
OH1–
nitrate
NO31–
nitrite
NO21–
bicarbonate
HCO31–
permanganate MnO41–
perchlorate
ClO41–
chlorate
ClO31–
chlorite
ClO21–
hypochlorite
ClO1–
2–
sulfate
sulfite
carbonate
chromate
dichromate
3–
SO4 phosphate
SO32–
CO32–
CrO42–
Cr2O72–
2–
PO43–
11. What is the only polyatomic ion that is a cation?
12. How are bicarbonate and carbonate related?
13. Predict the chemical formula and charge for the bisulfate ion.
14. How are chromate and dichromate related?
Polyatomic Ions
3
15. Bromine forms polyatomic ions with structures similar to those of chlorine. Using the chlorine
family of polyatomic ions as a model, predict the name of the BrO41– ion.
16. Identify the polyatomic ion in each of these ionic compounds. Write out the name and formula
of the ions including their charges.
a. CaCO3
b. Mg(OH)2
c. NH4Cl
Model 3 – Ternary Ionic Compounds
Compound Name
Ion Symbols and Charges
Chemical Formula
Ammonium phosphate
NH41+
PO43–
(NH4)3PO4
Barium nitrite
Ba2+
NO21–
Ba(NO2)2
Ammonium sulfate
NH41+
SO42–
(NH4)2SO4
Aluminum carbonate
Al3+
CO32–
Al2(CO3)3
Iron(III) hydroxide
Fe3+
OH1–
Fe(OH)3
Potassium nitrate
K1+
NO31–
KNO3
17. How are ternary ionic compounds in Model 3 different from binary ionic compounds (NaCl,
MgO, CaBr2, etc.) that you’ve seen previously? Hint: Consider the meaning of the word
“binary.”
18. Consider the compound iron(III) hydroxide in Model 3.
a. How many hydroxide ions (OH1–) are combined with an iron(III) ion (Fe3+)?
b. Is your answer to part a the only combination of iron(III) and hydroxide that should exist in
nature? Explain.
19. Consider the compound barium nitrite in Model 3.
a. What does the subscripted “2” inside the parentheses of the chemical formula tell you about
the compound?
Ba(NO2)2
↑
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POGIL™ Activities for High School Chemistry
b. What does the subscripted “2” outside the parentheses of the chemical formula tell you about
the compound?
Ba(NO2)2
↑
20. How many atoms of each element are in one formula unit of ammonium phosphate, (NH4)3PO4?
nitrogen
hydrogen
phosphorus
oxygen
21. A student writes the chemical formula for the ionic compound calcium hydroxide as CaOH2.
a. Write the chemical formula for each ion in the compound.
Calcium:
Hydroxide:
b. Why is the student’s chemical formula for the compound calcium hydroxide wrong?
22. Many of the chemical formulas in Model 3 include parentheses. Which one of the following rules
summarizes the appropriate use of parentheses in ternary ionic compounds? For the three rules
that do not apply in all cases, show at least one counter example from the chemical formulas in
Model 3.
Parentheses are used around any ion that is used more than once in a formula unit.
Parentheses are used around any polyatomic ion.
Parentheses are used around any polyatomic ion used more than once in a formula unit.
Parentheses are only used around polyatomic anions used more than once in a formula unit.
23. Write chemical formulas for the following ternary ionic compounds.
a. Calcium sulfate
b. Copper(II) nitrate
c. Lithium phosphate
d. Potassium permanganate
e. Aluminum sulfite
f. Magnesium bicarbonate
Polyatomic Ions
5
24. Name the following ternary ionic compounds.
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a. BaSO4
b. NH4NO3
c. K2Cr2O7
d. Fe(NO3)3
e. Mg(CH3COO)2
f. Al2(CO3)3
POGIL™ Activities for High School Chemistry
Extension Questions
25. If you were asked to go to the chemical storage area and retrieve a bottle of “sulfate,” could you
do so? Explain. (Assume you have permission from your teacher to go into the storage area.)
26. When asked to classify sodium acetate (NaCH3COO) as either an ionic or covalent compound,
a student responded with, “Sodium acetate is both ionic and covalent.” Explain why the student
gave this answer.
Polyatomic Ions
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