Chapter 4: Naming Compounds

Ionic Compounds

Naming Compounds

HW: Read 4.1 Do Sec. 4.1 Review Questions p. 108

Ionic CompoundsA chemical compound must have a net charge

of zero.

So if a compound contains ions, then:

1. Both positive ions (cations) and negative ions (anions) must be present.

2. The numbers of cations and anions must be such that the net charge is zero.

Ionic Compounds

Give the formula for each compound:

a) Ca2+ and Cl-

b) Na+ and S2-

c) Ca2+ and P3-

Old Names from an Old Time

When chemistry was an infant science, each chemical compound was given a different name.

-sugar of lead

-quicklime

-laughing gas

Why would it not be a good idea to give each compound a

different name?Because there are over four million chemical

compounds!

So instead of naming each compound, we now have a system for naming those compounds.

Not only should we be able to name compounds given their formulas, but we should be able to write their formulas given their names.

Naming Compounds with a Metal and a Nonmetal

Binary Ionic Compounds - A two-element compound consisting of a cation and an anion.

To name these compounds, we just use the name of the ions.

Cations’ Charges: Type ISome metal atoms form only one cation;

meaning, they will only lose a set number of electrons.

For instance, the Na atom always forms Na+.Na atoms will never form:

Na2+ or Na3+

Any compound containing this type of metal atom is a “Type I binary compound.”

Cations’ Charges: Type IISome metal atoms form more than one

cation; meaning, they can lose different numbers of electrons (the metal can have different charges).

For instance, the Cu atom can form Cu+ and Cu2+

Any compound containing this type of metal atom is a “Type II binary compound.”

How do you know if it’s I or II?

– Type I compounds • Metal present forms only one cation

– Type II compounds • Metal present can form 2 or more cations with

different charges

From the periodic table (p.79)

Memorize These!!!

Naming Type I Binary Ionic Compounds

Name These…

a) NaI

b) CaO

c) BaS

d) AlCl3e) Rb2O

Ionic Compounds and Ions

When ions are in an ionic compound, we do not write their charges.

When ions are shown individually, we write their charges.

Naming Type II Binary Ionic Compounds

Since the metal ion can have more than one charge, a Roman numeral is used to specify the charge.

Naming Type II Binary Ionic Compounds

Name the following:

a) FeCl2

b) PbO2

c) CuF

d) CoCl3

Naming CompoundsRemember, metals that form only one

cation do not need Roman numerals.

a) SnI4

b) KN

c) HgO

d) RbF

e) CrF2

f) MgBr2

Naming Binary Compounds that contain only Nonmetals

• These are called “Type III” binary compounds.

Prefixes for Numbers

Prefixes for Numbers

To avoid awkward pronunciations, we often drop the final o or a of the prefix when the second element is oxygen.

CO = “carbon monoxide”

Practice Naming

a) PCl5b) P4O6

c) SF6

d) SO3

e) SO2

f) N2O5