SIMPLY PUT, THE ART OF WRITING FORMULAS AND

NAMING CHEMICALS

CHEMICAL NOMENCLATURE

Writing Formulas• Binary ionic compounds• Ternary ionic compounds• Binary molecular compounds• Acids

Ionic Compounds• Composed of oppositely charged ions• Positive ion is a cation• Negative ion is an anion• Cations attract anions until the net

(overall) charge on the formula unit is zero

Properties of Ionic Compounds

• Usually solid at room temperature

• Are brittle and break under stress

• Usually soluble in water• Conduct when melted or

dissolved• Have high melting points

Binary Ionic Compounds• Contain a metal, written first, always positive,

from left of stairs on the periodic table (it may sometimes have a roman numeral for its charge

• Contain a nonmetal, written second, always negative, from the right of stairs on the periodic table, ends in -ide

• The oppositely charged ions attract each other until the net charge is 0.

Binary Ionic Formulas

Calcium oxide (metal / non-metal) Find calcium and its charge Ca+2

Find oxide and its charge O-2

To complete the formula, the charges must be completely balanced for a net charge of zero. Ca+2 O-2

The formula is: CaO

Another formula:

Aluminum sulfide (metal / nonmetal)

Find aluminum and its charge Al+3

Find sulfide and its charge S-2

To complete the formula, use the crisscross method and drop the signs:

Al+3 S-2

The formula is: Al2S3

Another one:• Copper (II) nitride (roman numeral tells

the charge!!!!!! It could be a +2 or a +1)• So Cu+2 for the first ion• And N-3 for the second ion• Cu3N2 is the resulting formula

Try these:

• Lithium sulfide Li2S

• Magnesium nitride Mg3N2

• Barium oxide BaO• Copper (II) bromide CuBr2

• Manganese (IV) oxide Mn2O4 = MnO2

• Iron (III) chloride FeCl3• Calcium selenide CaSe

Ternary Ionic Compounds• Consist of three or more elements. • Contain at least one polyatomic ion

which is a group of atoms with a charge such as sulfate, SO4

-2.

• Polyatomic ions usually end in -ate, -ite and sometimes -ide as in cyanide and hydroxide and are on the back of the periodic table.

Ternary Ionic Formulas

Lithium nitrate (metal / polyatomic ion)

Find lithium and its charge Li+1

Find nitrate and its charge NO3-1

To complete the formula, the charges must be completely balanced for a net charge of zero. (criss-cross, drop +/-)

The formula is: LiNO3

Another formula:Calcium nitrate (metal / polyatomic ion)

Find calcium and its charge Ca+2

Find nitrate and its charge NO3-1

To complete the formula, use the crisscross method and drop the signs. If the polyatomic ion has an added subscript, use parentheses around it.

(NO3)2

The formula is: Ca(NO3)2

Try these:

Potassium chlorate KClO3

Strontium nitrate Sr(NO3)2

Copper (II) sulfate CuSO4

Rubidium phosphate Rb3PO4

Aluminum chromate Al2(CrO4)3

Iron (III) cyanide Fe(CN)3

Ammonium sulfide (NH4)2S

Binary Molecular Compounds

• Contain two nonmetals• Nonmetals are located to the right of

the stairs on the periodic table• They share electrons in a covalent

bond to form molecules.

Properties of Molecular Compounds

• Usually gases at room temperature

• Are soft solids under stress• Usually soluble in water• Do not conduct when melted

or dissolved• Have low melting points

Binary Molecular Formulas

Dinitrogen pentoxide (non-metal / non-metal)

The prefix for each non-metal tells how many atoms of each element are present in the formula. It gives the subscript.

“di” means a subscript of 2 after nitrogen N2

“pent” means a subscript of 5 after oxygen O5

The formula is: N2O5

Try these:

Dichlorine heptoxide Cl2O7

Diphosphorous trioxide P2O3

Carbon tetrabromide CBr4

Dinitrogen tetrahydride N2H4

Carbon disulfide CS2

Boron trichloride BCl3

Naming Compounds These are the types:

A) Binary Ionic Compounds Metal with one possible charge Metal with two or more possible charges

B) Ternary Compounds

C) Binary Molecular Compounds

D) Acids

Binary Ionic Compounds (with fixed oxidation state on metal)• the metal has one possible charge and is

combined with a nonmetal

• Step #1: Name of Element with Positive Charge

• Step #2: Add Name of Negative element modifying ending to “ ide ”

Examples - Binary Ionic with one possible charge on the metal

• Al2S3 aluminum sulfide

• CaBr2 calcium bromide

• Mg3N2 magnesium nitride

• NaCl sodium chloride

Binary Ionic Compounds (with variable oxidation state on the metal)• the metal with several possible charges and is

combined with a nonmetal

• Step #1: Name of Element with Positive Charge followed by the Roman numeral for its charge

(I, II, III, IV, V, VI, VII, VIII, IX, X)

• Step #2: Add Name of Negative element modifying ending to “ ide ”

Examples - Binary Ionic with several possible charges on the metal

• CuCl2 copper (II) chloride

• CuCl copper (I) chloride

• Fe3N2 iron (II) nitride

• VBr5 vanadium (V) bromide

Ternary Ionic Compounds

• Step #1: Write name of the ion having positive charge. If it is a metal, check to see if it has fixed or variable charge. If variable, it must have a roman numeral!

• Step #2: Add name of the negative polyatomic ion WITHOUT changing its ending.

Examples of Ternary Ionic Compounds

• Zn (NO3)2 zinc nitrate

• Cs C2H3O2 cesium acetate

• Cr SO4 chromium (II) sulfate

• NH4 Cl ammonium chloride

• (NH4)2 SO3 ammonium sulfite

Additional Examples – Roman Numerals

• Fe (ClO3)3 Iron (III) chlorate

• Cu(NO3)2 Copper (II) nitrate

• Mn SO4 Manganese (II) sulfate

Review of all Ionic Compounds

Name the following ionic compounds:

BaS barium sulfide

K2SO4 potassium sulfate

PbO lead (II) oxide

Cu(NO3)2 copper (II) nitrate

AlN aluminum nitride

(NH4)2CrO4 ammonium chromate

Binary Molecular Compounds• Consist of two nonmetals• Write the name of the first element then the

second element, changing its ending to –ide.• Place prefixes in front of each element, indicating

the number of atoms of each element in the formula. One exception, never use mono- in front of the name of first element.

CO2 CO

carbon dioxide carbon monoxide

• The list of prefixes is on the back of your periodic table!!!

• Check it out!

Examples of Binary Molecular

• CBr4 carbon tetrabromide

• Cl2O7 dichlorine heptoxide

• N2O5 dinitrogen pentoxide

Formulas for Acids• Hydrosulfuric acid (hydro- tells you it is

binary!, sulf tells the second part) H+1 with S-2 and the formula is H2S

• Sulfuric acid ( ternary, no hydro, ic ending tells sulfate) H+1 and SO4

-2 combine for H2SO4

• Sulfurous acid (ternary, no hydro, ous tells sulfite) H+1 and SO3

-2 combine for H2SO3

Properties of Acids• Are corrosive - will cause burns• React with metals• Neutralize bases• Dissolve in water• Have a pH less than 7 on the pH scale• Taste sour like a lemon

Try These!Hydrochloric acid __________________

Chloric acid __________________

Chlorous acid __________________

Hypochlorous acid__________________

Perchloric acid __________________

Naming Acids• Acids start with hydrogen and are followed by an anion.

Use the root of the anion and change it in the following manner:

• Anion ending “ide” start with “hydro” root of anion followed by “ic” acid

HCl hydrochloric acid• Anion ending “ate” start with root of anion, followed by “ic”

acid

HClO3 chloric acid

• Anion ending “ite” start with root of anion, followed by “ous” acid

HClO2 chlorous acid

Examples of Naming Acids• H2Se hydroselenic acid

• H2SO3 sulfurous acid

• HNO3nitric acid

Examples of Naming Acids• HBr hydrobromic acid

• HClO4 perchloric acid

• HClOhypochlorous acid

Try These!

• H2S __________________

• H2SO4 __________________

• H2SO3 __________________

PROBLEM SOLVING• In this chapter you will have to solve the

following problems:

1. Find the percent composition of a material

2. Determine the empirical formula (simplest)

3. Determine the molecular formula (actual)

Acids: Know these!!!!• HCl• HNO3

• H2SO4

• H3PO4