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Section 6.3 Ionic Bonding and Ionic Compounds

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Warm-Up

How is a chemical formula for a covalent compound different from the chemical formula for an ionic compound?

Ionic Compounds

Made up of positive ions (cations) and negative ions (anions) that are combined so that the numbers of positive and negative charges are equal.

The chemical formula of an ionic compound represents the simplest ratio of the compound’s combined ions.

CrystalsCrystals

Most ionic compounds Most ionic compounds are are crystalline solids - crystalline solids - a three-dimensional a three-dimensional network of positive and network of positive and negative ions mutually negative ions mutually attracted to one another.attracted to one another.

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Formula Units Unlike molecular compounds, ionic compounds are

not made up of independent units that can be isolated and examined

Ionic solids exist as repeating units of positively and negatively charged ions in a 3-dimensional structure.

Formula units are the simplest collection of atoms from which an ionic compound’s formula can be established and that gives electrical neutrality

Calcium fluoride, CaF2 (fluorite)

Monatomic Ions

By gaining or losing electrons many main group elements form ions with noble gas configurations.

Ions formed from a single atom are called monatomic ions.

There is a PATTERN for which charge will form on an atom for the main groups.

+1 }SKIP+2 +3+4-4 -3 -2 -1 0

Formulas for Ionic CompoundsFormulas for Ionic Compounds

The charges must balance to 0, and the formula must reflect this.

Ionic compounds do not form by the combination of isolated ions, but we can use electron dot notation to see the changes that take place in ionic bonding.

Li and F LiF Mg and F MgF2

Formulas for Ionic CompoundsFormulas for Ionic Compounds

In your table groups come up with rule(s) for writing chemical formulas for ionic compounds.

Li and F LiF Al and O Al2O3

Li and O Li2O Al and F AlF3

Mg and F MgF2

Mg and O MgO

Rule???Rule???

Crisscross the charges!Crisscross the charges! Write the symbol for each ion, metals Write the symbol for each ion, metals

first.first. Write the charge above each.Write the charge above each. If the charges add up to zero, you’re If the charges add up to zero, you’re

done.done. If they don’t, play the criss-cross game.If they don’t, play the criss-cross game. Example:Example:

LiLi++ OO2- 2- = Li = Li22OO

Your TurnYour Turn

Write the formula for the following:

a.a. Li and S Li and S

b.b.Al and OAl and O

c.c. I and KI and K

d.d.Mg and FMg and F

e.e. N and AlN and Al

f.f. Ca and BrCa and Br

Li2S

Al2O3

KI

MgF2

AlN

CaBr2

What’s in a name?Activity Directions:

1.In your table groups, examine the table on page 2 and come up with at least three rules for naming ionic compounds based on the examples given.

2.Answer the making sense question and practice problems #1-6 and 1-8.

3 Rules?

• Positive ion (metal) always comes first

• Change ending of nonmetal to –ide

• Add Roman numerals to show the charge on transition metals

Name the following ionic compounds:

1. NaCl

2. K2S

3. Ca3N2

4. FeS

5. CoF2

6. ZnCl2

Sodium Chloride

Potassium Sulfide

Calcium Nitride

Iron (II) Sulfide

Cobalt (II) Fluoride

Zinc (II) Chloride

Actually just Zinc Chloride b/c Zinc only has 1 possible charge

Write the following ionic compounds:

1. Magnesium iodide

2. Lithium bromide

3. Calcium Phosphide

4. Aluminum Nitride

4. Aluminum Chloride

5. Potassium Oxide

6. Iron (III) Sulfide

7. Copper (II) Chloride

MgI2

LiBr

Ca3P2

AlN

AlCl3

K2O

Fe2S3

CuCl2

Check-in:

• Write the symbols for the cation and anion in the ionic compound PbCl4 and name the compound.

Pb4+ and Cl1- Lead (IV) Chloride

1. Name the following binary ionic compounds.

a. K3Nb. CoF2

c. PbI2

d. SnS2

e. NiOf. ZnCl2g. Ag3P

Homework #1-2

Potassium nitrideCobalt (II) Fluoride

Lead (II) IodideTin (IV) SulfideNickel (II) OxideZinc (II) Chloride

Silver (I) Phosphide

2. Write the formulas for the following names:

a. Magnesium iodideb. Lithium bromidec. Aluminum chlorided. Calcium phosphidee. Potassium oxidef. Iron (III) sulfideg. Copper (I) Chlorideh. Gold (III) iodidei. Zinc (II) oxide

MgI2

LiBrAlCl3Ca3P2

K2OFe2S3

CuClAuI3

ZnO

Monotomic IonsMonotomic Ions

Ions formed from a Ions formed from a single atom. single atom. Main Main group ions form to group ions form to a noble gas a noble gas configuration:configuration:

AlAl3+3+, O, O2-2-, etc., etc.Transition metals can Transition metals can

show many different show many different charges: Pbcharges: Pb2+2+, Pb, Pb4+4+, , etc.etc.

Ratios To balance the charge, the ratio of the ions in a

formula unit depends on the charges of the combined ions.

Example: Names – cation first, anion last. Calcium fluoride (the -ine of the anion is dropped and replaced by -ide as a suffix because the fluorine is now in an ionic compound).

Ca2+ + 2F- → CaF2

Naming Binary Ionic Compounds

Nomenclature: naming system.

We will go over the Stock System of Nomenclature (Chapter 7, Section 1, pp. 206-210).

You MUST use Table 7-1 p. 205 and Table 7-2 p. 210 to

help you in naming ionic compounds.

Polyatomic IonsPolyatomic Ions

Consist of more than Consist of more than one atom and the one atom and the group is charged:group is charged:

NHNH44++, SO, SO44

2-2-, etc., etc.

Formation of Ionic CompoundsFormation of Ionic Compounds• Ionic compounts do not form by the

combination of isolated ions, but electron dot notation can be used to demonstrate the changes that take place.

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Mama Nature Strikes Again

Since nature favors situations of lowered potential energy, ions do this by arranging into an orderly 3-D arrangement known as a crystal lattice.

Structure:Structure:

3-D crystals 3-D crystals balancebalance + and -charges + and -charges ex. Naex. Na1+1+ClCl1- 1- = NaCl, = NaCl,

CaCa2+2+ 2F 2F1-1- = CaF = CaF22

The ions in the crystal are surrounded The ions in the crystal are surrounded by ions of opposite charge.by ions of opposite charge.

Energy is released Energy is released

when ions form bonds.when ions form bonds.

Lattice EnergyLattice Energy This is the This is the

energy released energy released when one mole when one mole of an ionic of an ionic crystalline crystalline compound is compound is formed from formed from gaseous ions gaseous ions (see table 6-3 on (see table 6-3 on p. 179).p. 179).

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Ionic vs. Molecularbonding:

Very strong, hard and brittle.

Solids at room T Higher bp/mp Conduct heat & electricity

in molten state. Many soluble in water.

Strong within molecule; weak between molecules.

Mostly gases and liquids @ room T (vaporize readily)

Lower bp/mp. Don’t conduct.

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Polyatomic Ions

Groups of covalently bonded atoms can have charges.

Ex. PO43−

The phosphate anion is a covalently bonded molecule that has gained 3 electrons and has become an ion. It is able to bond with another ion such as Fe2+ to give Fe3(PO4)2 [iron (II) phosphate].

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Assignment:Worksheets:

6-3 Review

Chapter 6 Review, pp. 195-198, 11, 19, 35-39, 41, 42, 54, 56, 57, 63-65.

Do all assignments from the book separately.