chalifoux.cachalifoux.ca/ShepNet/Sci10/Sci10text/Chapter 2/Section 2.1 Pg 42.pdf · Copper can fonn the cations Cu+ and Cu2+.lfyou are given the fonnula of an ionic compound, you

2.1

Do you enjoy a sip of refreshing dihydrogen monoxide on a hot day? Do youlike sodium chloride on your French fries? Do you take sucrose in your tea?You probably know these substances better as water, salt, and sugar - their

common names. Figure 2.1 shows some other examples of chemicals withcommon names.

Common names often tell very little about a substance. In the past, namesoften referred to the source, uses, or properties of a substance. Saltpetre, forexample, is a salty-tasting chemical found crusted on rocks (petra in Greek).No one could guess from this name that saltpetre is a potassium compound.Chemists need a naming system that lets them identify the substance clearly.A chemical name also should describe the composition of a substance. Aswell, it should enable chemists to communicate results with other chemistsaround the world.

A Sodium hydrogen carbonate,NaHCO3, is commonly calledbaking soda. It is often placed inrefrigerators to prevent odours.The baking soda absorbs moistureand molecules that cause odourfrom the air.

B Solid carbon dioxide, CO2, is often called dry ice becauseit resembles solid water (ice). Unlike ice, it does not melt undernormal conditions. Instead, dry ice sublimes to form gaseouscarbon dioxide.

C Limestone, used for building, is composed mainly of calciumcarbonate, CaCO3. Calcium carbonate also has the commonnames chalk or calcite.

Each of these compounds has a common name, asystematic name, and a chemical formula. Which do you think ismost useful in identifying the compound?

42 MHR . Unit 1 Energy and Matter in Chemical Change

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The international system for naming chemicals is maintainedby the International Union of Pure and Applied Chemistry(IUPAC). Founded in 1919, IUPAC has developed a systematicmethod to name chemicals according to their composition.

Today, chemists allover the world use the IUPAC system.This system ensures that each pure substance has a single,unique name, called its systematic name. The name of asubstance describes its composition. It also enables you towrite its chemical formula and predict some of its properties.For example, the systematic name for saltpetre is potassiumnitrate (KNO3). This name identifies the substance as an ioniccompound that contains potassium and nitrate ions. From thisinformation, a modem chemist can predict that, like all potassiumsalts, potassium nitrate will dissolve readily in water.

In this section, you will learn how to name several types of compoundsfrom their formulas. You will also learn how to write a chemical formula whenyou are given the name of a compound. Later, you will study properties ofdifferent types of compounds.

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Binary CompoundsCompounds that are made up of two elements are called binary compounds.Sodium chloride, NaCI, is a binary compound. The same is true of nitrogendioxide, NOl. Compounds that contain atoms of more than two elementsare not binary compounds. For example, sodium nitrate, NaNO3, is not a binarycompound. One way to identify a binary compound is to examine the endingof its name. The names of binary compounds that you will see in this textbook almost

always end with the suffix "-ide."

?Before chemical names werestandardized. a single compoundmight have more than one name.For example, sulfur dioxide (802)was known as both vitriolic acidair and sulfurous gas.

Table 2.1 Prefixes for BinaryMolecular CompoundsI,

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Binary Molecular CompoundsA binary molecular compound fonns whenatoms of two different elements group togetheras molecules by forming covalent bonds. Usuallythe two elements are non-metallic elements. Thesethree rules will help you write the names andfonnulas of binary molecular compounds. !

1. The first element in the name and fonnula is usually the one that isfarther to the left on the periodic table. For example, in a compoundcontaining carbon and oxygen, the carbon is named first because carbonis to the left of oxygen on the periodic table.

2. The suffix "-ide" is attached to the name of the second element. Forexample, in a compound containing carbon and oxygen, the name"oxygen" is changed to "oxide."

3. Prefixes are used to indicate how many atoms of each type are presentin one molecule of the compound. Table 2.1 lists the first ten prefixes.For example, a compound consisting of molecules with one carbonatom and two oxygen atoms is called carbon dioxide.

Chapter 2 Names, Formulas, and Properties. MHR 43

Study Table 2.2 to understand how to apply these rules. Table 2.2 listsdifferent binary molecular compounds formed from nitrogen and oxygen.

Table 2.2 Naming the Oxides of Nitrogen

~ Car exhaust is a

Pause&== - Reflect I

Look back to Figure 1.28 on page31. The figure shows the crystallattice for sodium chloride, NaCI.Copy the figure into your note-book. Circle a portion of thecrystal lattice that represents oneformula unit of sodium chloride.

Names and Formulas for Binary Ionic CompoundsA binary ionic compound is composed of ions of one metal element and ions of onenon-metal element joined by ionic bonds. The name of a binary ionic compoundis formed from the names of its elements. These three rules can help youwrite the names and formulas of binary ionic compounds.

1. The first element in the name and formula is the metal.

2. The second element, the non-metal, is named as an ion. In other words,the suffix "-ide" is attached to the name. For example, the compoundformed from lithium and fluorine is named lithium fluoride.

3. The chemical formula shows the simplest whole number ratio of eachtype of ion in the compound. For example, the formula CaF2 indicatesthat any crystal of calcium fluoride contains two fluoride ions for everycalcium ion.

Note that because ionic compounds are crystal lattices, their formulas do notrepresent molecules. Instead, the formulas represent the smallest repeating unitwithin the lattice. These repeating units are called fonnula units.


mixture of gases that includescarbon monoxide and carbondioxide. For carbon monoxide,CO, carbon is to the left of oxygenin the periodic table, so it comesfirst in both the name and formula.The "di-" prefix of carbon dioxide,CO2, you now know.

Cation ChargesAtoms of some elements can fonn more than one ion. For example, most of thetransition metals (the elements in groups 3 to 12 on the periodic table) are ableto fonn more than one cation. The periodic table in Appendix B shows somecommon ions of the transition metals. For example, nickel can fonn the cationsNi2+ and Ni3+. Copper can fonn the cations Cu+ and Cu2+.lfyou are giventhe fonnula of an ionic compound, you can determine the charge on the cation.

Naming Cations Using the Stock SystemThe current way to distinguish between cations was invented by a Germanchemist, Alfred Stock. In the Stock system, the charge on the cation is written,in parentheses, as a Roman numeral after the name of the metal. (The first tenRoman numerals are I, II, ill, Iv; V; VI, VII, VIII, IX, and X.) For example,Cu+ is called copper(I). Cu2+ is called copper(Il).

The Stock system is used only for metals that have more than one type ofcation. You do not need to write sodium(I), because sodium forms only onetype of cation: Na+. When an ionic compound is named using the Stocksystem, the name tells you the cation charge to use.


Pause& ;

~ Reflect

You may need to write the formulafor an ionic compound withoutknowing the Stock name. In thatcase, choose the most commoncation, as indicated on the periodictable in Appendix B. For example,suppose you were asked to writethe formula for an ionic compoundcontaining mercury and iodine. Thebest answer is Hg12, because Hg2+is a more common ion than Hg+.Now write the formula for anionic compound containing leadand bromine.

In Investigation 2-A, you will practise using the rules for writing namesand formulas of binary ionic compounds.

11The classical system for naming transition metal cations is basedon the Latin names for metals. For example, the Latin names for iron,copper, and lead are ferrum, cuprum, and plumbum. To indicate theion with the higher charge, the "um" ending is dropped, and the suffix"-ic" is added. The suffix "-ous" indicates the ion with the lower charge.Copy and complete the table below by adding the missing names.The first line is given to help you.

The classical system for

naming compounds is still

used. Compare the Stock

system with the classical

system. Which do you think

works better, and why?

Chaoter 2 Names. Formulas. and Prooemes . MHR 47

Think About ItIonic bonding involves the transfer of electrons toform ions with the same electron configuration asa noble gas. In this investigation, you will use theperiodic table to predict the number of electronstransferred in the formation of some binary ioniccompounds. Then, you will use this information todetermine the chemical formula of each substance.

. Examine the type of elements in each ofthe following substances. Identify whethereach name or formula represents an ionicor molecular substance.

(a) sodium sulfide

(b) PCl3(c) nitrogen dioxide

(d) zinc oxide

(e) MgIzApparatusperiodic tablenotebook 0 Remember dIat dIe name of a binary ionic

What to Do0 Review the definition of a binary compound on

page 43. Then, identify the binary compounds inthe following list:

(a) HCI

(b) SO3

(c) MgCO3(d) hydrogen sulfide

(e) sodium hydrogencarbonate

0 Copy the formulas below. Find the total chargeon the cations and the total charge on the anions.Classify each formula as correct or incorrect.Correct the incorrect formulas. Finally, writethe name of each compound.

(a) LiD

(b) MgO

(c) K2S

(d) AlBr3

(e) NaN3

. As you have seen, the naming system for ionicsubstances differs from the naming system formolecular substances.(a) Which types of elements combine to form

binary ionic compounds?(b) Which types of elements combine to form

molecular compounds?


compound begins with the name of its cation(metallic) and ends with the name of its anion(non-metallic). The anion name ends with "-ide."Copy the table below and use this informationto complete it.

~ Copy and complete the following table by addingthe missing Stock system names. The first line isgiven to help you.

Stock System Naming

(8 Write the chemical formula for each of the

following compounds.(a) copper(I) oxide

(b) lead(IV) bromide

(c) iron(III) sulfide

(d) nickel(IlI) fluoride

(e) manganese(IV) sulfide

~ When the Stock system is used to name an ioniccompound, you can tell immedicately whichcation charge to use. Copy the following example,then move on to question 12.

Q) What happens when you do not have the Stockname of an ionic substance to help you write itsfonnula? In that case, choose the most commoncation of the transition metal, as indicated on theperiodic table in Appendix B. Write fonnulas torepresent the following compounds, choosingthe most common cation.

(a) an ionic compound containing ironand chlorine

(b) an ionic compound containing titaniumand fluorine

(c) an ionic compound containing platinumand oxygen

(d) an ionic compound containing leadand oxygen

Writing a chemical formula given the Stock system nameof a compound

In iron(ll) sulfide, the iron cation must be Fe2+. 2-According to the periodic table, the sulfur anion is S .

For the compound to be electricallyFe2 + 52 - neutral, there must be one iron ion

for each sulfur ion.

Fe5 iron(ll) sulfide

Check your answer by adding the total charges onthe ions. +2 + (-2) = 0The total charge is zero. The answer is correct.


Table 2.3 Common Polyatomic Ions

NH4+

OH-

C032-

N03-

S042-

HC03-

HS04-

P043-

ammonium

hydroxide

carbonate

nitrate

sulfate

hydrogencarbonate

hydrogensulfate

phosphate

Compounds Containing Polyatomic IonsMany ionic compounds are not binary because one or both ions contain atomsof more than one element. These polyatomic ions consist of one or moredifferent atoms, which are joined by covalent bonds. As a group, these bondedatoms have an overall positive or negative charge. An example of a polyatomicion is the nitrate ion, NO3-. In the nitrate polyatomic ion, one nitrogen atomand three oxygen atoms are joined by covalent bonds. As a unit, they have a netcharge of 1-. Many common polyatomic ions are negatively charged and havenames ending in "ate." You will find it helpful to memorize the names, formulas,and charges of the ions shown in Table 2.3. You will find the names, formulas,and charges of more polyatomic ions on the periodic table in Appendix B.

Compounds containing polyatomic ions are classified as ionic. To name thesecompounds, use the name of the cation, followed by the name of the anion. Forexample, ~O3 is named ammonium nitrate. men writing formulas, youmust use parentheses around the polyatomic ion when more than one is presentin a formula unit. For example, aluminium nitrate must contain three nitrateions, NO3-, for every aluminium ion, Al3+. This combination gives a netcharge of zero. To show this clearly, the formula is written Al(NO3)3. ModelProblems 4 and 5 below give more examples of writing names and formulasfor compounds that contain polyatomic ions.

IrWhat is the formula of atnmoniutn sulfide? . '

Compounds with polyatomicions contain both ionic andcovalent bonds. For example,sodium sulfate, Na2S04,is classified as an ionicsubstance because it ismade up of different ions.Sodium sulfate dissolvesin water, and the solutionconducts electricity. Becausethe sulfate ion, S042-, ismade up of non-metal atoms,however, the bondingbetween the sulfur andoxygen atoms is covalent.

SolutionThe compound contains a polyatomic ion, so it is ionic. Name itwithout using prefixes. Write the formula of each ion:NH + 52-

4

Since the compound must be electrically neutral, there must be twoammonium ions for every sulfide ion.Use parentheses to indicate the two ammonium ions present.

The formula of ammonium sulfide is (NH4)25

Check your answer by adding the total charges on the ions.[2 X (+1)] + (-2) = 0The total charge is zero. The answer is correct.

What is the name of CUCO3?

SolutionFrom the periodic table in Appendix B, the two possible ions of copper areCu+ and Cu2+. From Table 2.3 above, the carbonate ion has a charge of2-.Cu? CO 2-

3

There is one copper ion and one carbonate ion in each formula unit ofCUCO3. Since the compound must be electrically neutral, the copper ionmust be Cu2+.The name of CUCO3 is copper(II) carbonate.

. MHR 51C:h"nter Name.- FOnlllua.- and Pronertie

Table 2.4 A Family ofOxygen-Containing Anions

Families of Polyatomic AnionsYou may have noticed that many polyatomic anions are composed of oxygenand one other non-metallic element. Nitrate, N03-, and sulfate, 5042-, are twocommon examples. Nitrite, N02-, and sulfite, 5032-, are two other examples.What do you notice about the names, formulas, and charges of the nitrateand nitrite anions? What do you notice about sulfate and sulfite?

Anions that contain oxygen, such as sulfate and sulfite, or nitrate and nitrite,are part of the same families of polyatomic anions. They contain the sameelements and have the same charge. Their names and formulas are slightlydifferent, however. You can use a series of rules to name anions that belongto these families. The rules are Qutlined below.

. In each family, the anion with the ending "-ate" serves as a reference point.In the example in Table 2.4, nitrate, N03-, is the reference. The other anionsare named according to the number of oxygen atoms in their formula, inrelation to the reference anion.

. Compared with an "_ate" anion, an anion named "_ite" has one lessoxygen atom in its formula. Compare nitrate, N03-, with nitrite, N02-.

. Anions that have two less oxygen atoms than the reference anion are named

"hypo_ite", as in hyponitrite, NO-.. Anions that have one more oxygen atom than the reference anion are called

"per_ate", as in pernitrate, N04-.

52 MHR . Unit I Energy and Matter in Chemical Change

Answer the following questions. They will help you practise naming oxygecontaining anions based on the rules you have just learned.

17. The anion sulfate has the formula 5042-. What is the formulaand charge of the sulfite anion?

18. The anion chlorate has the fonnula CIO3and charge of the hypochlorite anion?

What is the formula

The anion iodate has the formula 103charge of the periodiate anion?

What is the formula and19.

Find Out

2. Prepare cards and a detailed set of rules for

your game.

The Ionic Card Game ~

How well do you understand the rules for classify-ing and naming ionic compounds? In the followingactivity, apply your knowledge to design a chemical

card game.3. Try several rounds of your game within your

group. Refine the rules as necessary.

Materials

pencilsfelt markersindex cards

4. Exchange games with at least one other group.After playing each game, complete an evalua-tion of the game as directed by your teacher.

What Did You Find Out? . r~1!1!~1!\~"iiJJ !:.11!~ !'i!li[;I~:i:;Jii'!!11~

2. How did your game differ from those of

other groups?

3. What would you improve about your gameif you were to redesign it? Give reasons for

each change.

4. How has producing and playing a card gamehelped you learn and practise naming rulesand formula-writing rules for ionic compounds?

and Prooerties . MHR 53tlanter 2 Name Irlnul:

1. What were the main difficulties your groupfaced in designing and producing the game?1. Work with your group to design a card game

that involves naming and finding formulas forionic compounds. Consider the followingpoints as you design your game.

. Your game must include a variety of ions,

including polyatomic ions, and mustinvolve combining them to make formulaunits with a net charge of zero.

. The game must include at least 32 cards.

. You may base the game on other cardgames, or you may invent a new

game entirely.. The game should involve two to four

players and require no more than 15 minto complete.

Hydrogen CompoundsOne important group of compounds seems to break thenaming rules given in this section. You might think thatHCI, for example, would be ionic. It contains hydrogen(found with the metals on the periodic table) and a non-metal. In fact, hydrogen is a non-metal, and HCI is knownto be molecular. It is the same for most other compoundswhose names begin with "hydrogen". The names of thesemolecular substances, however, do not use prefixes. The

correct name for the molecular compound HCI is hydrogenchloride, not hydrogen monochloride. Similarly, HzS is hydrogen

sulfide, not dihydrogen monosulfide. You will learn more aboutthis type of substance in section 2.3. Compounds containing hydrogen

and carbon, such as ethane, CZH6, or ethanol, CzHsOH, have another set ofnaming rules, which you will learn in later science courses.

Table 2.5 shows some examples of important compounds that contain hydro-gen. You should memorize the names and formulas of these common compounds.

Table 2.5 Selected Hydrogen-Containing Compounds

Section 2. 1 SummaryIn this section, you learned how to name and write formulas for ionic andmolecular compounds. Table 2.6 below summarizes some of the key pointsto remember when naming molecular compounds and ionic compounds.Table 2.6 A Summary

of Key Naming Rules


Check Your Understanding1. Name each of the following ionic compounds:

(a) MgBr2(b) KHSO4

(c) <NH4)3PO4

(d) Ca(OH)2

2. Name each of the following molecular compounds:

(a) CF4 (d) PCl3

(b) PH3 (e) N2F4

(c) P4010 (1) 02F2

3. Copy the following list of compounds in your notebook. Identify eachcompound as ionic or molecular. Mark the binary compounds with anasterisk (*). Name each compound using the appropriate method.

(a) P20S

(b) CaSO4(c) KNO3 ~-~

(d) Mgh

4. Write the formula for each of the following compounds:

(a) phosphorus pentachloride(b) sulfur hexafluoride

(c) nitrogen trifluoride

(d) silicon tetrafluoride

(e) silver phosphate

(1) manganese(Il) dichromate

(g) sodium perchlorate

(h) cobalt(Il) permanganate

5. Write the systematic name for each of the following substances:

(a) water, H2O

(b) ammonia, NH3

(c) potash, K2CO3(d) lye, NaOH

6. Thinking Critically Explain why a standard naming system is importantfor international communication, safety, and efficiency.

Chapter 2 Names, Fonnulas, and Properties. MHR 55

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chalifoux.cachalifoux.ca/ShepNet/Sci10/Sci10text/Chapter 2/Section 2.1 Pg 42.pdf · Copper can fonn the cations Cu+ and Cu2+.lfyou are given the fonnula of an ionic compound, you