Roy Kennedy

Massachusetts Bay Community College

Wellesley Hills, MA

Introductory Chemistry, 3rd Edition

Nivaldo Tro

Chapter 5

Molecules and

Compounds (Part 2)

2009, Prentice Hall

5.6 Nomenclature: Naming

Compounds

• This will be on quiz 5

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Formula-to-Name

Step 1

Is the compound one of the

exceptions to the rules?

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Common Names—Exceptions

• H2O = Water, steam, ice.

• NH3 = Ammonia.

• CH4 = Methane.

• NaCl = Table salt.

• C12H22O11 = Table sugar.

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Formula-to-Name

Step 2

What major class of compound is it?

Ionic or Molecular?

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Classifying Ionic or Molecular• Ionic compounds.

Metal + nonmetal(s) – Binary ionic

Type I cation – charge known

Type II cation – charge must be given

Compounds with polyatomic ions.

• Molecular compounds.

2 or more nonmetals.

Binary molecular (or binary covalent) 2 nonmetals..

Acids—Formula starts with H combined with a anion

either monoatomic or polyatomic ion.

Molecular when pure

Ionic when dissolved in water.

May be binary or oxyacid.

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Formula-to-Name

Step 3

What major subclass of compound is it?

Binary Ionic, Ionic with Polyatomic Ions,

Binary Molecular,

Binary Acid, or Oxyacid?

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Classifying Compounds

• Compounds containing a metal and a nonmetal = Binary ionic.

Type I and II.

• Compounds containing a polyatomic ion = Ionic with polyatomic ion.

• Compounds containing two nonmetals = Binary molecular compounds.

• Compounds containing H and a nonmetal = Binary acids.

• Compounds containing H and a polyatomic ion = Oxyacids.

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Formula-to-Name

Step 4

5.7 Ionic Compounds

5.8 Molecular Compounds

5.9 Acids – Molecular compounds that behave

like ionic compounds in water

5.7 Naming Ionic Compounds

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Types of Ionic Compounds

• Monoatomic cation (metal) and

monoatomic anion (nonmetal)

Cations with only one charge – Type I – Main

group and Ag+ and Zn2+

Cations with more than one charge – Type II –

usually transition metals and some heavier main

group elements

• Polyatomic ion present (KNOW THE

POLYATOMIC IONS FROM THE WEB)Tro's "Introductory Chemistry",

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Formula-to-Name

Rules for Ionic

• Made of cation and anion.

• Name by simply naming the ions.

If cation is:

Type I metal = Metal name.

Type II metal = Metal name (charge).

Polyatomic ion = Name of polyatomic ion.

If anion is:

Nonmetal = Stem of nonmetal name + -ide.

Polyatomic ion = Name of polyatomic ion.

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Monatomic Nonmetal Anion• Charge from periodic table

• To name anion, take the root of the element

name and add the suffix–ide.

• Group 5A Group 6A Group 7A

N3- nitride O2- oxide F- fluoride

P3- phosphide S2- sulfide Cl- chloride

Br- bromide

I- iodide

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Metal Cations• Type I

one possible charge.

1A, 2A, (Al, Zn, Ag).

Charge by position on the periodic table.

1A = +, 2A = 2+, Al = 3+.

Some need to be memorized.

Zn = 2+, Ag = +.

• Type II

Metals whose ions can have more than one possible charge.

Determine charge by charge on anion.

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Type I Binary Ionic Compounds

Formula Cation name Anion name

CaF2 calcium fluoride

K2S potassium sulfide

NaBr sodium bromide

Al2S3 aluminum sulfide

MgO magnesium oxide

Note: no numerical prefixes are used.

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Type II Binary Ionic Compounds

• Cation name (charge as Roman numeral) + anion

name

• Charge is determined from anion

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Determining the Charge on a Variable

Charge Cation—NiCl2 and Fe2S3

1. Ni?+ + 2 Cl-

2. The Ni charge must balance the anions total 2 x (-1) = -2

3. Ni is 2+ nickel(II)chloride

1. Fe2S3 2Fe?+ + 3 S2-

2. The Fe charge balances the anions. 3 x (-2) = =6

3. Fe is 3+, 2 x (+3) = 6 iron(III)sulfide

Another way to work out the

charge• Reverse the method of crossing the charges

Cu2O Cu21+ O 2- copper(I)oxide

Be careful because a common factor may have

been divided out

PbO2 – uncrossing the charges leads to Pb2+ and

O - -, but O is actually O2- . Two O2- is -4

This compound is actuall Pb 4+ lead(IV)oxide

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Compounds Containing

Polyatomic Ions

• Name of cation Type I or Type II rules. + name

of anion.

The polyatomic ions you need to

know are on the stuff you must

memorize web page

Stuff you must memorize

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Writing Names for an Ionic Compound Containing

Polyatomic Ion,

Iron(III) phosphate

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Type I

NaNO2 sodium nitrite

Ca(NO3) 2 calcium nitrate

Al2(PO4) 3 aluminum phosphate

Type II

Pb(ClO4) 2 lead(II)perchlorate 2 ClO4- means Pb is 2+

CuSO4 copper (II)sulfate 1 SO42- means Cu is 2+

Fe2(PO4) 3 iron(III) phosphate 2 PO43- means Fe is 3+

5.8 Naming Molecular

Compounds

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Formula-to-Name

Rules for Molecular

• Only for 2 elements binary.

• For binary molecular:

numerical first numerical root

Prefix + element + prefix + second + -ide

(omit if 1) name element

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Numerical Prefixes

• 1 = mono-

Not used on first nonmetal.

• 2 = di-

• 3 = tri-

• 4 = tetra-

• 5 = penta-

• 6 = hexa-

• Drop last ―a‖ if name begins with vowel.

Binary Molecular Compounds

of Two Nonmetals

• SO3 sulfur trioxide

• CS2 carbon dioxide

• S4N4 tetrasulfur tetranitride

• SF6 sulfur hexafluoride

• P2O5 diphosphorus pentaoxide

5.9 Naming Acids

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Formula-to-Name

Acids• Acids have formulas that start with H and contain

an anion either monoatomic or polyatomic

• Acids are molecular, but when dissolved in water they for ions H+ cation(s) and an anion(s).

Binary acids monoatomic ion

• Hydro- prefix + stem of the name of the nonmetal + -ic suffix + acid.

HCl hydrochloric acid

HBr hydrobromic acid

HI hydroiodic acid

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Polyatomic ion acid• Oxyacids:

If polyatomic ion ends in –ate = Name of polyatomic ion with –ic suffix + acid.

If polyatomic ion ends in –ite = Name of polyatomic ion with –ous suffix + acid.

Acid anion name

HNO3 nitrate nitric acid

H2SO3 sulfite sulfurous acid

HClO4 perchlorate perchloric acis

H2CrO4 chromate chromic acid

H3PO4 phosphate phosphoric acid

H3PO3 phosphite phosphorus acid

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Naming compounds from formula

• Decide if common name

• Classify as Ionic or Molecular

• Ionic –

Type I or II cation

Monoatomic or polyatomic ion

• Molecular

Binary

Acids

Binary

OxyacidsTro's "Introductory Chemistry",

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Naming examples

• Ca(ClO4)2 calcium perchlorate

• NH3 ammonia

• P4S5 tetraphosphorous pentasulfide

• HClO3 chlorous acid

• Na2S sodium sulfide

• CoCl3 cobalt(III)chloride

• HBr hydrobromic acid

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5.10 Nomenclature Summary

• An excellent summary of naming

compounds is Figure 5.17 on page 143.

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