Chapter 8.

Chemical Nomenclature

Chemical nomenclature is the system of names used to distinguish chemical compounds from each other, and the rules needed to devise these names.

Chemical Nomenclature

Why Bother?

How do you speak Al2(SO4)3 ?

What system do we use?

IUPAC International Union of Pure and Applied Chemistry

Chemical Nomenclature

Three major categories of compounds:

Ionic

First element in formula is a metal.

Molecular

First element in formula is a nonmetal.

Acid

First element in formula is Hydrogen.

Naming Ionic Compounds

Types of ionic compounds:

Binary, contains two elements:

NaCl, MgBr2, Fe2O3

Ternary, contains three elements; two are in a polyatomic anion:

NaNO3, NH4Cl, Cr2(SO4)3

Naming Binary Ionic Compounds

What is the charge on the metal ion?

Fixed: Group 1A, +1; Group 2A, +2

Al3+, Ga3+, Zn2+, Cd2+, Ag1+

Examples: NaCl, Al2O3, CdS

Name cation as element, e.g. sodium

Name anion with stem of element name, followed by suffix ide, e.g. chloride

Naming Binary Ionic Compounds

What is the charge on the metal ion?

Variable: All other metals

Examples: CuO, FeBr2, Fe2O3

Name cation as element, followed by charge in Roman numerals, enclosed by parentheses, e.g. copper(II)

Name anion with stem of element name, followed by suffix ide, e.g. oxide

Naming Binary Ionic Compounds

What is the charge on the metal ion?

The compound must be electrically neutral.

Use the charge on the anion to figure out the charge on the metal.

Examples: FeO, Fe2O3

CuCl, CuCl2SnF2, SnF4

Hg2Cl2, HgCl2

Naming Binary Ionic Compounds

An older naming system gives the suffix ic to the ion with the higher charge, and the suf-fix ous to the ion with the lower charge, following the (usually Latin) element stem.

FeO ferrous oxide; Fe2O3 ferric oxide

CuCl cuprous chloride CuCl2 cupric chloride

SnF2 stannous fluoride SnF4 stannic fluoride

Hg2Cl2 mercurous chloride HgCl2 mercuric chloride

Naming Ternary Ionic Compounds

Name metal as you would for a binary, with charge if necessary.

Name anion as itself. Know these:

CO32- carbonate ClO1- hypochlorite

NO31- nitrate ClO3

1- chlorate

PO43- phosphate C2H3O2

1- acetate

SO42- sulfate CH3COO1- acetate

OH1- hydroxide CN1- cyanide

Naming Ternary Ionic Compounds

There is one polyatomic cation

NH41+, ammonium

Name it, then name anion properly

Formulas from Names

Write symbol for metal ion first, then anion.

Use the charges on the ions to determine how many of each ion are present in the formula. Charges must sum to zero.

If a polyatomic ion appears more than once in a formula, enclose it in parentheses, followed by a subscript showing the number of times the ion occurs in the compound.

Practice

Give Name Give Formula

CaCl2 Mercurous iodide

Mg(NO3)2 Mercury(II) iodide

Al2(SO4)3 Silver nitrate

FeCl3 Ammonium bromide

AgBr Tin(II) hydroxide

MnO2 Sodium cyanide

NH4NO3 Calcium phosphate

Naming Molecular Compounds

These are all binary. Since the atoms do not have charges, use Greek numerical prefix-es to indicate the number of each atom in the molecule.

Know these:

1 mono 4 tetra

2 di 5 penta

3 tri 6 hexa

Naming Molecular Compounds

How to name them: 1. Prefix for first element in formula, omit if it's "mono"2. Name first element2. Prefix for second element in formula,3. Give stem of second element followed

by suffix ide.CO Carbon monoxide

CO2 Carbon dioxide

N2O Dinitrogen monoxide

Naming Molecular Compounds

Details and exceptions:

If last letter of prefix for number and first letter of element are both vowels, drop the last letter of the prefix:

CO carbon monoxide

N2O5 dinitrogen pentoxide

Some compounds are known only by common names.

H2O water NH3 ammonia

Formulas from Names

Write symbol for least electronegative element first, then most electronegative.

Use prefixes to determine subscripts in formula.

Metalloids are not metals, and their com-pounds are named as molecular com-pounds.

Practice

Give Name Give Formula

NO2 Carbon tetrachloride

SO3 Phosphorus trichloride

SiO2 Selenium dibromide

TiO2 Dinitrogen tetroxide

NO Sulfur dioxide

P2O5 Xenon tetrafluoride

Fe2O3 Diantimony Trioxide

Naming Acids

Types of acids:

Binary, contains two elements:

HCl, HBr, H2S

Ternary, contains three elements; two are in a polyatomic ion:

HNO3, H2SO4, H3PO4

Naming Binary Acids

Binary acids are gases as pure compounds.

Symbol: HCl or HCl (g)

Name: hydrogen + stem of nonmetal followed by suffix -ide.

hydrogen chloride

Naming Binary Acids The compounds become acidic in water

solution (aqueous solution); they ionize.

HCl + H2O H3O1+ + Cl1-

H3O1+ is what makes acids acidic.

Symbol: HCl (aq)

Name: prefix hydro- + stem of nonmetal followed by suffix -ic acid.

hydrochloric acid

Naming Ternary Acids

No distinction is made between pure ternary acids and those in aqueous (water) solution.

Symbol: H2SO4

Name: stem of central atom followed by suffix -ic acid.

sulfuric acid

Naming Ternary Acids

Know names of these ternary acids. They are related to "must know" polyatomic anions:

H2CO3 HClO

HNO3 HClO3

H3PO4 HC2H3O2

H2SO4 CH3COOHHOH HCN (aq)

Naming Acids and Anions

Useful Generalization:

If the name of an anion ends in -ide, its aqueous acid is named as hydrostemic acid.

If the name of an anion ends in -ate, its acid is named as stemic acid.

PracticeGive Name Give Formula

HBr (aq) Sulfuric acid

HNO3 Carbonic acid

H2O Hydrogen iodide

H2S Hypochlorous acid

HF Hydrocyanic acid

H3PO4 Acetic acid

HI (aq) Chloric acid

Naming Mixed Salts

Mixed salts are compounds in which Na1+ or K1+ combine with H1+ and an anion with -2 or -3 charge.

Symbol: KHSO4

Name: metal cation, hydrogen, anion

Potassium hydrogen sulfate

Naming Mixed Salts

If the anion has -3 charge (PO43-), three cations

are required to form a neutral compound.

Symbol: NaH2PO4

Name: metal cation, prefix di-hydrogen, anion Sodium dihydrogen phosphate

Symbol: K2HPO4

Name: prefix di-metal cation, hydrogen, anion Dipotassium hydrogen phosphate

More Practice

Give Name Give Formula

AgNO3 Magnesium sulfate

CaS Ferric chloride

NH3 Nitric acid

NaHS Lead(IV) sulfate

ZrO2 Sodium hydrogen carbonate

H2SO4 Mercuric bromide

Al2O3 Phosphorus trifluoride