NAMING IONIC COMPOUNDS

Chapter 6.3 Notes

Naming Ionic Compounds

1. Naming Ionic Compoundsa.The name of an ionic compound must

distinguish the compound from other ionic compounds containing the same elements.

b.The formula of an ionic compound describes the ratio of the ions in the compound.

Binary Ionic Compounds

2. Binary Ionic Compoundsa. A compound made from only two

elements is a binary compound.b. The pattern for naming binary

ionic compounds is the cation followed by the name of the anion.

Binary Ionic Compounds

i.The name for the cation is the name of the metal without any changes while the name of the anion uses part of the name of the nonmetal with the suffix –ide at the end.

Metals With Multiple Ions

3. Metals With Multiple Ionsa. When a metal forms more than

one ion, the name of the ion contains a Roman numeral to indicate the charge on the ion.

Metals With Multiple Ions

b. Ex.1) Copper(I) Oxide VS. Copper(II) Oxidei. The chemical formula for

copper(I) oxide is Cu2O because

it takes two Cu1+ ions to balance the charge on an O2- ion.

Metals With Multiple Ions

ii. The chemical formula for copper(II) oxide is CuO because it takes only one Cu2+ ion to balance the charge on an O2- ion.

Polyatomic Ions

4. Polyatomic Ionsa. A covalently bonded group of

atoms that has a positive or negative charge and acts as a unit is a polyatomic ion.

b. The prefix poly means many.

Polyatomic Ions

c. Ex. 2) Iron(III) Hydroxide

i. Chemical formula = Fe(OH)3,

The parentheses and subscript 3

indicates that there are three hydroxide ions for each iron (III) ions.

Writing Formulas for Ionic Compounds

5. Writing Formulas for Ionic Compoundsa. If you know the name of an ionic

compound, you can write its formula.b. Place the symbol of the cation first,

followed by the symbol of the anion.

Writing Formulas for Ionic Compounds

c. Use subscripts to show the ratio of the ions in the compound.

d. Because all compounds are neutral, the total charges on the cations and anions must add up to zero.

Writing Formulas for Ionic Compounds

e. Ex. 3) Sulfur and Sodiumi. There must be two sodium ions

(Na+) for each sulfide ion (S2-). The

formula for sodium sulfide is Na2S.

The 2- charge on one sulfide ion is balanced by the 1+ charges on two sodium ions.

Ex. 4) Write the formula for the compound calcium chlorideWhat Do I Know?

The name of the compound is calcium chloride.

What Do I Need To Know?The chemical formula for calcium chloride.

Plan and Solve:1. List the symbols and charges

for the cation and anion. Ca with a charge of 2+ and Cl

with a charge of 1-.2. Determine the ratio of ions in

the compound. It takes two 1- charges to

balance the 2+ charge. There will be two chloride ions for each calcium ion.

3. Write the formula for calcium chloride.

CaCl2

 

Ex. 5) Write the formula for the compound calcium oxide

What Do I Know?The name of the compound is calcium oxide.

What Do I Need To Know?The chemical formula for calcium oxide.

Plan and Solve:1. List the symbols and charges

for the cation and anion. Ca with a charge of 2+ and O

with a charge of 2-.2. Determine the ratio of ions in

the compound. It takes one calcium ion with a

charge of 2+ to balance one oxide ion with a charge of 2-.

Answer:3. Write the formula for

calcium oxide. CaO

 

Ex. 6) Write the formula for the compound copper(II) sulfide

What Do I Know?The name of the compound is Copper(I) sulfide.

What Do I Need To Know?The chemical formula for copper(I) sulfide.

Plan and Solve:1. List the symbols and charges

for the cation and anion. Cu(I) with a charge of 1+ and

Sulfide with a charge of 2-2. Determine the ratio of ions in

the compound. Two copper(I) ions, each with

a charge of 1+ , balance one sulfide ion with a charge of 2-.

3. Write the formula for calcium chloride.

Cu2S

Ex. 7) Write the formula for the compound sodium sulfate

What Do I Know?The name of the compound is Sodium Sulfate.

What Do I Need To Know?The chemical formula for Sodium Sulfate.

Plan and Solve:1. List the symbols and charges

for the cation and anion. Sodium with a charge of 1+

and sulfate with a charge of 2-.1. Determine the ratio of ions in

the compound. Two sodium ions, each with a

charge of 1+, balance one sulfate ion with a charge of 2-.

1. Write the formula for sodium sulfate.

Na2SO4

Describing Molecular Compounds

6. Describing Molecular Compoundsa. In naming molecular compounds the

focus is on the composition of molecules.b. The name and formula of a molecular

compound describe the type and number of atoms in a molecule of the compound.

Describing Molecular Compounds

c. In naming molecular compounds the most metallic element appears first in the name. These elements are farther to the left and bottom of the periodic table.

d. You first must add the proper prefix to each element. The prefix tells us how many atoms of each element there are.

e. The name of the second element ends in ide. Such as Carbon Dioxide.

Number of Atoms Prefix

1 Mono-2 Di3 Tri-4 Tetra5 Penta6 Hexa7 Hepta8 Octa9 Nona-10 Deca

Example 8

Name the compound N2O4.• There are two nitrogen atoms

and four oxygen atoms. Therefore the name is dinitrogen tetraoxide.

Example 9

Name the compound NO2.• There is one nitrogen atom and two

oxygen atoms. Therefore the name is mononitrogen dioxide. However the prefix mono- is generally not used, therefore the name is nitrogen dioxide.

Example 10

Write the formula for diphosphorus tetrafluoride.• Since di- means two and tetra

means four the formula is P2F4.