Understanding Ionic Compounds: Formulas, Names, and Charges

1. Chapter 5 Types of Compounds 5.1 Ionic Compounds 5.2 Molecular Substances

2. 5.1 Ionic Compounds - Objectives • Apply ionic charge to writing formulas for ionic compounds • Apply formulas to name ionic compounds • Interpret the information in a chemical formula

3. Formula and Names of Ionic Compounds • Ionic compounds are composed of ions bound by ionic bonds usually a metal and a nonmetal • Ionic bonds are strong attractive forces • Ionic compounds are usually solids at room temperature • Many are crystalline • Difficult to melt  high melting points • When melted or in solutions they conduct electricity

4. Binary Ionic Compounds • Binary compound- composed of two elements • Binary ionic compounds- composed of two different ions • NaCl • KI • CaF2

5. Ions • Positively charged = cation • When naming the name stays the same • Calcium ion • Sodium ion • Negatively charged = anion • When naming the name is changed • Ending becomes –ide • Chloride ion • Sulfide ion

6. Naming Binary Ionic Compounds • Always write the cation first followed by the anion. • Make sure the anion ending is modified to –ide. • Na+ + Cl- Sodium Chloride • K+ + I-  Potassium Iodide

7. Writing Binary Ionic Compound Formulas • Compounds are always neutral • Net ionic charge must always be zero • Use subscripts to indicate when more than one ion of an element is present • When only one ion is present, no subscript is needed • NaCl • When more than one is present subscripts are need • CaF2 1 Calcium ion and 2 fluoride ions

8. Binary Ionic Compounds • Always written in the smallest whole number ratio – Formula Unit • Example Calcium Fluoride

9. Predicting Charges on Ions • Oxidation Number- the charge on the ion • Metals always lose electrons when they form ions • Nonmetals always gain electrons when they form ions • Periodic table can be used to predict the oxidation number (charge of ion) of some elements

10. Table 5.1 Ionic Charges of Representative Elements

11. Let’s Try It! • Write the formula for an ionic compound containing sodium and sulfur. • What is the name of the compound?

12. Write a formula for each of the following compounds • Lithium oxide • Calcium bromide • Sodium oxide • Aluminum sulfide

13. Write the formula & name for the compound formed from each of the following pairs of elements. • Barium and oxygen • Strontium and iodine • Lithium and chlorine • Radium and chlorine

14. 5.1 Ionic Compounds

15. Compounds Containing Polyatomic Ions • Polyatomic Ions-an ion that has two or more different elements • Group of atoms are covalently bonded together when the atoms share electrons • The individual atoms do not have a charge, but the group as a whole has an overall charge

16. Polyatomic Ions • Ionic compounds may contain positive metal ions bonded to negative polyatomic ions or negative nonmetal ions bonded to positive polyatomic ions

17. Writing formulas using Polyatomic Ions • Treat the polyatomic ion as one unit or a single ion • Write the cation ion first followed by the anion • When more than one polyatomic ion is needed to make the net charge zero you place it in parentheses and then add the subscript.

18. Common Polyatomic Ions

19. Naming Polyatomic Ions • Follows the same rules as naming binary • Name the cation first and then the anion • You do not change the ending of the anion for polyatomic ions • -ite indicates one less oxygen atom than -ate • -ate indicates one more oxygen atom than –ite • Does not tell you the number of oxygen atoms in the ion

20. Let’s Try It! • Write the formula for the compounds made from each of the following ions. • Ammonium and sulfite ions • Calcium and hydrogen phosphate ions • Ammonium and dichromate ions • Barium and nitrate ions

21. Let’s Try It! • Write the formula for each of the following compounds. • Sodium phosphate • Magnesium hydroxide • Ammonium phosphate • Potassium dichromate

22. Compounds of Transition Elements • Transition elements are groups 3 through 12 in the periodic table • Form positive ions, but they form more than one type of positive ions • Copper forms two ions one with a +1 charge and one with a +2 charge • The way they are distinguished is with roman numeral. Copper (I) and Copper (II)

23. Names of Common Ions of Selected Transition Elements

24. Let’s Try It! • Write the formula for the compounds made from each of the following pairs of ions. • Copper (I) and sulfite • Tin (IV) and fluoride • Gold (III) and cyanide • Lead (II) and Sulfide

25. Let’s Try It! • Write the names of the following compounds. • Pb(NO3)2 • Mn2O3 • Ni(C2H3O2)2 • HgF2

26. Hydrates • Many ionic compounds are prepared by crystallization from a water solution, and water molecules become a part of the crystal. • Hydrates- a compound in which there is a specific ratio of water to ionic compound. • In hydrate, the water molecules are chemically bonded to the ionic compound

27. Hygroscopic • Hygroscopic- a substance that absorbs water molecules from the air to become a hydrate. • Sodium Carbonate • Some substances are so hygroscopic that they take up enough water from the air to dissolve completely and form a liquid solution. These compounds are called deliquescent. • Sodium Hydroxide

28. Writing Formulas for Hydrates • When writing a formula for a hydrate you place a dot in the formula between the ionic compound and the water. • CaSO4· 2H2O • What this means is for every one calcium sulfate there are two water molecules in the hydrate.

29. Naming Hydrates • You use the regular name for the compound followed by the word hydrate, to which a prefix is added. • 1 = mono- • 2 = di- • 3 = tri- • 4 = tetra- • Exp.: CaSO4· 2H2O  Calcium sulfate dihydrate

30. Anhydrous • Anhydrous – a compound in which all the water has been removed, usually by heating • In some cases the anhydrous compound may be a different color than the hydrate. • Copper (II) sulfate pentahydrate is blue compound when it is heated to remove the water and become anhydrous it turns white, this compound is Copper (II) sulfate anhydrous

31. Homework • P. 184-185 #1-5, 7, 8