Section 7.2

Ionic Bonds

And

Ionic Compounds

Formation of an Ionic Bond

Compound

A chemical combination of two or more different elements

Binary compounds when there are exactly two different elements

Formation

P. 210 shows chemical reactions that form ionic bonds and release energy

a. Sodium and chlorine gas produce a white crystalline solid

Na + Cl Na+ + Cl- + energy

This is called a chemical equation.

What Happened?

Sodium transferred one valence electron to chlorine.

+ [Na]+ + [Cl]- + energy

This is the electron-dot structures

Types of Ionic Compounds

Electrostatic force holds the charged atoms together is the ionic bond.

Metal and non-metal ionic bond are called oxides.

Most other ionic compounds are called salts.

Names

Sodium + Chlorine forms sodium chloride

Sodium is a metal

Chlorine is a non-metal

Change chlorine to chloride in the name of the compound

p. 210 b

• Ribbon of magnesium metal burns in air, it forms the ionic compound magnesium oxide.

• Magnesium is a metal

• Oxygen is a non-metal

Notice the name, oxygen became oxide.

Is this a binary ionic compound?

Questions

Explain how an ionic compound forms from these elements

7. sodium and nitrogen

8. lithium and oxygen

9. strontium and flourine

10. aluminum and sulfur

Challenge Question

11. Explain how elements in group 1 and group 15 combine to form an ionic compound.

Properties of Ionic Compounds

Physical structure

• Ratio of positive and negative ions

• Ions are packed into repeating pattern

• Balance the forces of attraction and repulsion between ions

* No single unit of Na and Cl exists, there are many Na+ and Cl- ions in a 1 to 1 ratio.

Question

What determines the ratio?

Common Ionic Compounds

• Carpet: calcium carbonate• Ceramics/glass: calcium carbonate, lithium

borate, magnesium silicate, sodium carbonate• Glossy Paper: aluminum silicate, calcium

carbonate, sodium sulfate, calcium oxide, sodium carbonate, titanium(IV) oxide

• Toothpaste: calcium carbonate, sodium carbonate, sodium-hydrogen carbonate, sodium fluoride

Crystal Lattice

Three dimensional geometric arrangement of particles

Each positive ion is surrounded by negative ions and each negative ion is surrounded by positive ions

The number of ions and the ratio determine the size and shape

Examples

Minerals

More than 1/3 of all known minerals are silicates

Halides

Borates

Carbonates

What elements do you think are in these?

Physical Properties

• Melting point• Boiling point• Hardness

Depends on how strong the ionic attraction is

Ionic crystals are hard, rigid, brittle solids, hard to break apart – high melting and boiling points

• Conduct electricity

Solids: ions are locked into place, cannot conduct electricity

Melt or dissolve solids into solutions

Electrolytes are solutions that conduct electricity and important to humans

Energy

Endothermic

Energy is absorbed

Exothermic

Energy is released

Formation of ionic compounds

Forms more stable system so lower

energy state, release energy

Math / Graph

Make a scatterplot of Interionic Distance and Lattice Energy

(μm)

(kJ/

mol

)

Title_______________

Lattice Energy and Interionic Distance

Ionic Radius: the sum of the radii of each ion

Li+: 76 μm

F-: 133 μm

Cl-: 181 μm

I-: 220 μm

Find

LiF, LiCl, LiI

Lattice Energy

LiF: -1032 kJ/mol

LiCl: -852 kJ/mol

LiI: -761 kJ/mol

Plot each ionic compound

Use a different color for each point and label

Relationship

Use your graph to describe the relationship between the interionic distance and lattice energy.

Fill in the blanks:

As interionic distance ________, lattice energy ___________.

Lattice Energy

• Energy required to separate 1 mol of the ions in an ionic compound

• The greater the lattice energy, the stronger the force of attraction ( harder to separate)

Predict

Use your graph to estimate the lattice energy for LiBr.

The ionic radius of Br- is 196 μm.

Patterns in Lattice Enery

Make a line graph of compound versus lattice energy (kJ/mol)

Make each set of compoundsa different color, 4 colors

Li set – blueNa set – redK set – greenRb set - orange

Compound Lattice Energy

LiF

LiCl

LiBr

LiI

-1032

-852

-815

-761

NaF

NaCl

NaBr

NaI

-926

-786

-752

-702

KF

KCl

KBr

KI

-813

-717

-689

-649

Make each set of compounds a different color

Li set – blueNa set – redK set – green

Write a few sentences to describe any pattern you see.

Prediction

• Predict the shape of the graph of the lattice energies of

• RbF, RbCl, RbBr, RbI

Add to Graph in Orange

• Add the Rb___ compounds to your graph in orange to verify your prediction.

• RbF 774

Summary

• Ionic compounds contain ionic bonds formed by the attraction of oppositely charged ions.

• Ions in a ionic compound are arranged in repeating patterns known as a crystal lattice.

• Ionic compounds properties are related to ionic bond strength.

• Ionic compounds are electrolytes; they conduct an electric current in the liquid phase and in aqueous solution.

• Lattice energy is the energy needed to remove 1 mol of ions from its lattice.

Questions

12.Explain how an ionic compound made up of charged particles can be neutral?

13.Describe the energy change associated with ionic bond formation, and relate it to stabillity.

14. Identify three physical properties of ionic compounds that are associated with ionic bonds, and related them to bond strength.

15.Explain how ions form bonds, and describe the structure of the resulting compound.

16.Relate lattice energy to bond strength.17.Use electron configurations, orbital

notations and electron dot structures to represent the formation of an ionic compound from the mental strontium and the non-metal chlorine.

Question

Using the elements aluminum and oxygen, determine the formula for the ionic compound.

Extension: Use Fe2+ and Fe3+ to combine with O2-

Determine the formula for the ionic compounds.

Each Student

List a metal and a non-metal

Exchange papers and determine the ionic compound formed between them.

Exit Ticket

• Determine the ionic compound formed from Mg and Cl and explain how it was formed.

• Include its ratio