Formation and Properties of Ionic Compounds

1. Section 7.2 Ionic Bonds And Ionic Compounds

2. Formation of an Ionic Bond Compound A chemical combination of two or more different elements Binary compounds when there are exactly two different elements

3. Formation P. 210 shows chemical reactions that form ionic bonds and release energy • Sodium and chlorine gas produce a white crystalline solid Na + Cl  Na+ + Cl- + energy This is called a chemical equation.

4. What Happened? Sodium transferred one valence electron to chlorine. [Na]+ + [Cl]- + energy + This is the electron-dot structures

5. 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.

6. 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

7. 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?

8. Questions Explain how an ionic compound forms from these elements • sodium and nitrogen • lithium and oxygen • strontium and flourine • aluminum and sulfur

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

10. 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.

11. Question What determines the ratio?

12. 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

13. 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

14. Examples Minerals More than 1/3 of all known minerals are silicates Halides Borates Carbonates What elements do you think are in these?

15. 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 Physical Properties

16. Endothermic Energy is absorbed Exothermic Energy is released Formation of ionic compounds Forms more stable system so lower energy state, release energy Energy

17. Math / Graph Make a scatterplot of Interionic Distance and Lattice Energy Title_______________ (kJ/mol) (μm)

18. 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 Lattice Energy and Interionic Distance

19. Relationship Use your graph to describe the relationship between the interionic distance and lattice energy. Fill in the blanks: As interionic distance ________, lattice energy ___________.

20. 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)

21. Predict Use your graph to estimate the lattice energy for LiBr. The ionic radius of Br- is 196 μm.

22. Patterns in Lattice Enery Make a line graph of compound versus lattice energy (kJ/mol) Make each set of compounds a different color, 4 colors Li set – blue Na set – red K set – green Rb set - orange

23. Make each set of compounds a different color Li set – blue Na set – red K set – green Write a few sentences to describe any pattern you see.

24. Prediction • Predict the shape of the graph of the lattice energies of • RbF, RbCl, RbBr, RbI

25. Add to Graph in Orange • Add the Rb___ compounds to your graph in orange to verify your prediction. • RbF 774

26. 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.

27. 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.

28. Questions • Explain how an ionic compound made up of charged particles can be neutral? • Describe the energy change associated with ionic bond formation, and relate it to stabillity. • Identify three physical properties of ionic compounds that are associated with ionic bonds, and related them to bond strength.

29. Explain how ions form bonds, and describe the structure of the resulting compound. • Relate lattice energy to bond strength. • 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.

30. 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.

31. Each Student List a metal and a non-metal Exchange papers and determine the ionic compound formed between them.

32. Exit Ticket • Determine the ionic compound formed from Mg and Cl and explain how it was formed. • Include its ratio