Section 7.3

Names and Formulas

For

Ionic Compounds

Naming Compounds

Name of a student _________ _________ first last

Name of an ionic compound sodium chloride

Which substance lost electrons?Which substance gained electrons?

Formula Unit

Chemical compound of an ionic compound

Simplest ration of the ions involved

Magnesium Chloride

Magnesium group 2 Mg2+

Chlorine group 17 Cl-

Want net charge of zero:

Have 2+ and 1-

Want 2+ and 2- so need 2 Cl-

Ratio 1:2 MgCl2

Ratios

Determine the ratio from the formula units

Ag2S

MgCl2

Al2O3

On Your Own

Determine the ratio

SnF4

FeO

Monatomic Ions

One-atom ion

Mg2+

Br-

Use the periodic table.

What is the formula for beryllium ion?

Iodide ion?

Nitride ion?

Common Monatomic Ions

Group Atoms Charge on Ions

1 H, Li, Na, K, Rb, Cs

1+

2 Be, Mg, Ca, Sr, Ba

2+

15 N, P, As 3-

16 O, S, Se, Te 2-

17 F, Cl, Br, I 1-

Monatomic Metal Ions

Group Common Ions

3 Sc3+, Y3+, La3+

4 Ti2+, Ti3+

5 V2+, V3+

6 Cr2+, Cr3+

7 Mn2+, Mn3+, Tc2+

8 Fe2+, Fe3+

Continued

Group Common Ions

9 Co2+, Co 3+

10 Ni2+, Pd2+, Pt2+, Pt 4+

11 Cu+, Cu2+, Ag+, Au+, Au 3+

12 Zn2+, Cd2+, Hg2+

13 Al 3+, Ga2+, Ga 3+, In+,In2+, In 3+, Tl+, Tl 3+

14 Sn2+, Sn 4+, Pb2+, Pb 4+

Oxidation Numbers

The charge on a monatomic ionOxidation number or oxidation state

Equals the number of electrons transferred from the atom to form the ion

Notice some ions have more than one oxidation state – with the d orbital elements

Binary Ionic Compounds

Symbol Cation then Anion

Subscripts equals number of ions

if no subscript then it is 1

How to figure the Formula

Write the symbol and charge for each ion

Find the ratio of ions in the formula

• Overall charge must be zero

• Subscripts times the charges sum to zero

Example 7.1

Determine the formula for the ionic compound formed from potassium and oxygen.

Potassium group 1 K+

Oxygen group 16 O2-

Ratio: 2:1

K2OEvaluate: 2 K ions (+1) + 1 O ion (-2)

= 2 (+1) + 1(-2) = 2 + (-2) = 0

Example 7.2

Determine the formula for the compound formed from aluminum ions and sulfide ions.

Aluminum group 13 Al3+

Sulfur group 16 S2-

Ratio: 2:3

Al2S3

Evaluate: 2 Al ions (3) + 3 S ions (-2)

= 2 (3) + 3 (-2) = 6 + (-6) = 0

Practice Write the ionic compound formula.19.Potassium and

iodide

20.Magnesium and chloride

21.Aluminum and bromide

22.Cesium and nitride

19. KI

20. MgCl2

21. AlBr2

22. Cs3N

Polyatomic Ionic Compounds

Ionic compounds made from more than one atom.

Popular ions

Ammonium NH4+

Nitrite NO2-

Nitrate NO3-

Hydroxide OH-

Cyanide CN-

Formulas for Polyatomic Ionic Compounds

Mg(NO3)2 Mg2+ + (NO3)- ratio 1:2

Al(NO3)3 Al3+ + (NO3)- ratio 1:3

Use parenthesis to surround the polyatomic ion

Practice

Write the formula for ionic compounds.

24. Sodium and nitrate

25. Calcium and chlorate

26. Aluminum and carbonate

24. Ratio 1:1

Na+ + (NO3)- Na(NO3)

25. Ratio 1:2

Ca2+ + (ClO3)- Ca(ClO3)2

26. Ratio 2:3

Al3++(CO3)2- Al2(CO3)3

Naming Ionic Compounds

1. Name the cation followed by the anion

2. For monatomic cations use the element name

3. For monatomic anions change the suffix to –ide.

CsBr Cesium Bromide

Rule 1

Rule 2Rule 3

4. To distinguish between multiple oxidation numbers of the same element use (roman numerals) after the symbol.

Fe2+ + O2- FeO Iron (II) Oxide

Fe3+ + O2- Fe2O3 Iron (III) Oxide

5. When the compound contains a polyatomic ions use the polyatomic ion name.

NaOH is sodium hydroxide (OH)-

(NH4)2S is ammonium sulfide (NH4)+

Naming Ionic Compounds

Determine the cation and anion

of the given formula

Does the cation haveonly one oxidation

number?

Write the name ofthe cation, then thename of the anion

Wite the name of thethe cation followed

by a Roman numeral to represent the charge, then

write the anion name.

Yes No

Practice Problems

Name the following compounds.

28.NaBr

29.CaCl230.KOH

31.Cu(NO3)2

32.Ag2CrO4

Each Student

Make a 5 x 5 chart

Across the top write 5 non-metal ions, with one polyatomic anion

Along the side list 5 metals, with ammonium ion.

Trade charts with another student, name each compound in the boxes.

Trade back and check.

Summary

A formula unit gives the ratio of cations to anions in the ionic compound.

A monatomic ion is formed from one atom. The charge of amonatomic ion is its oxidation number.

Roman numerals indicate the oxidation number of cations having multiple possible oxidation states.

Polyatomic ions consist of more then one atom and act as a single unit.

To indicate more than one polyatomic ion in a chemical formula, place parentheses around the polyatomic ion and use a subscript.

Practice Problems

34.State the order in which the ions associated with a compound composed of potassium and bromine would be written in the chemical formula and the compound name.

35.Describe the difference between a monatomic ion and a polyatomic ion, and give an example of each.

36. Ion X has a charge of 2+ and ion Y has a charge of 1-. Write the formula unit of the compound formed from the ions.

37.State the name and formula for the compound formed from Mg and Cl.

38.Write the name and formula for the compound formed from sodium ions and nitrite ions.

Exit Ticket

This is the formula for making artificial ocean water often used in saltwater aquariums. Mix 24.72g NaCl, 0.67g KCl, 1.36g CaCl, 4.66g MgCl2, 6.29g MgSO4 and 0.18g NaHCO3.

Name each ionic compound.