1. Chapter 5: Types of Compounds
Section 5.1: Ionic Compounds
  Chapter 5: Types of Compounds

2. Objectives: Apply ionic charge to writing formulas for ionic compounds, Apply formulas to name ionic compounds, Interpret the information in a chemical formula

3. Ionic Compound Formulas
BINARY COMPOUNDS: Contain only two elements
Can contain more than one ion of each element (ex: CaF2), but are not composed of three or more different elements.

4. Ionic Compound Formulas
Naming Binary Ionic Compounds: 1) Write the name of the positively charged ion (metal) 2) Add the name of the negatively charged ion (nonmetal), modified to end in –ide Ex: Potassium, Chlorine → Potassium Chloride Magnesium, Oxygen → Magnesium Oxide

5. Ionic Compound Formulas
Try these: 1) Li2O 2) CaCl2 3) Sulfur and Sodium 4) Potassium and Sulfur 5) Fluorine and Sodium

6. Formulas for Ionic Compounds
Compounds are electrically neutral – the sums of the charges in an ionic compound equal 0
Add subscripts to the element symbols (ions) until the sum of the ions’ charge is 0.
The smallest subscript is 1. However, no subscript needs to be written - the 1 is understood.
Example: NaCl - 1 Sodium, 1 Chlorine

7. Formulas for Ionic Compounds
If more than one ion of a given element is in a compound, the subscript indicates how many ions are present
Example: CaF2 - 1 Calcium, 2 Fluorine ions

8. Formulas for Ionic Compounds
In an ionic compound, a formula represents the smallest ratio of atoms or ions in the compound
Ex. CaF2 not Ca2F4
In a covalent compound, the smallest unit of the compound is a molecule
Ex. H2O
A formula is the simplest possible ratio of ions present.

9. Formulas for Ionic Compounds
FORMULA UNIT: Simplest ratio of ions in a compound.

10. Charges on Ions Metals tend to lose electrons and become positive ions
Nonmetals tend to gain electrons and become negative ions
OXIDATION NUMBER: Charge on an ion

11. Charges on Ions
Oxidation numbers for elements are can be predicted by group number.
Ex: F is in group 17, it gains one outer electron
Al is in group 13, it loses three outer electrons
However, oxidation numbers for elements in groups 3-12 (transition elements) cannot be predicted by group
Get out periodic table and make notes!

12. Writing a simple formula
Write the formula for an ionic compound containing sodium and sulfur. 1)What are the elements involved? 2) What are the oxidation numbers of each? 3) Sum of the ions must be zero. (add some if necessary 4) Write the symbols and numbers (subscripts) for each element, positive ion (metal) first.

13. Writing a simple formula
Practice Problems
lithium oxide
→ Li2O
2) calcium bromide
→ CaBr2
 3) barium and oxygen
→ BaO
4) strontium and iodine
→ SrI2

14. Writing a simple formula
More Practice 5) Barium and oxygen 6)Strontium and iodine 7) Lithium and chlorine 8) Radium and chlorine

15. Examples: nitrite NO22-, sulfate SO42-
POLYATOMIC ION
Ion that has 2 or more different elements
In a polyatomic ion, a group of atoms is covalently bonded together when the atoms share electrons.
Although the individual atoms have no charge the group as a whole has a charge.
Examples: nitrite NO22-, sulfate SO42-

16. POLYATOMIC ION Formulas for polyatomic ions:
Treat the polyatomic ion as if it were a single-element ion by keeping it together as a unit.
The sum must equal zero.
Multiples of a polyatomic ion in a formula can be indicated by placing the entire polyatomic ion in parentheses.
Example: Mg(NO3)2
Note: Never change the subscripts within the polyatomic ion

17. POLYATOMIC ION Sample problems 1) Write a formula for Li+ and CO32-
Because CO3 has a –2 charge, two Li are needed to balance
Li2CO3
Check charges: 2(1+) +1(2-) = 0 (sum must equal zero)

18. POLYATOMIC ION 2) Write a formula for Al3+ and SO42-
Find the least common multiple of 2 and 3 → 6
Two Al3+ will be needed: 2 (3+) = 6
Three SO42- will be needed: 3 (2-) = -6
Al2(SO4)3
Check charges: 2 (3+) + 3 (2-) = 0

19. POLYATOMIC ION 3) Ammonium (NH4+) and sulfite (SO32-)
Because SO3 has a –2 charge, two NH4 are needed to balance
(NH4)2SO3
Check Charges: 2 (1+) + 1 (2-) = 0

20. POLYATOMIC ION 4) Sodium (Na+) and Phosphate (PO43-)
Because PO4 has a –3 charge, 3 Na are needed to balance
Na3PO4
Check Charges: 3 (1+) + 1 (3-) = 0

21. POLYATOMIC ION
Formulas: 1) Aluminum and cyanide 2) Lithium and peroxide 3) Ammonium and phosphate 4) Calcium and carbonate 5) Rubidium and nitrate Names: 1) BaSO4 2) MgCO3 3) Li2SO3 4) K3PO4 5) Al(CN)3

22. Examples: Cu+ Cu2+ Fe2+ Fe3+
Transition Elements
Can have more than one oxidation number, except Zn2+ and Ag+ only have one type of ion
Examples: Cu+ Cu Fe2+ Fe3+
Show Video

23. Transition Elements Naming compounds formed from transition elements:
Use a Roman numeral to indicate the oxidation number of the transition element
Roman numerals are placed in parentheses after the name of the element
Examples: Cr2+ Chromium (II)
Cr3+ Chromium (III)
Cr6+ Chromium (VI)
Show Video

24. Transition Elements Examples
1) Write the formula for Copper (I) and Sulfite
Cu+ and SO32-
Because SO3 has a –2 charge, 2 Cu will be needed to balance
Cu2SO3

25. Transition Elements 2) Write the name for Pb(NO3)2
Because NO3 has a –1 charge and there are 2 of them, the oxidation state of Pb must be +2
lead (II) nitrate

26. Transition Elements Practice Problems: Gold (III) sulfate
Nickel (II) fluoride
MnS
Cu2SO3
SnF4
Au(CN)3

27. HYDRATE
Compound in which there is a specific ratio of water to ionic compound
In hydrates, the water molecules are chemically bonded to ionic compounds (• H2O)
Ex CuSO4 • H2O

28. HYDRATE
HYGROSCOPIC substances: Ionic compounds can easily become hydrates by absorbing water molecules from water vapor in the air
Example: Na2CO3
DELIQUESCENT substances: So hygroscopic that they take up enough water from the air to dissolve completely and form a liquid solution
Example: NaOH

29. HYDRATE
Compounds that form hydrates are often are used as drying agents (desiccants)
Heating hydrates can drive off water.
ANHYDROUS compound: One in which all of the water has been removed.

30. HYDRATE To write the formula for a hydrate,
1) Write the formula for the compound
2) Place a dot followed by the number of water molecules per formula unit of compound
Ex. CuSO4 • 5H2O

31. HYDRATE To name hydrates, 1) Write the regular name for the compound
2) Use prefix to indicate the number of water molecules present in front of the word hydrate
Ex Copper (II) sulfate pentahydrate

32. HYDRATE
Prefixes to Use in Naming Hydrates: Molecules of water Prefix 1 mono- 2 di- 3 tri- 4 tetra- 5 penta- 6 hexa- 7 hepta- 8 octa- 9 nona- 10 deca-

33. HYDRATE Examples: Calcium chloride pentahydrate
Aluminum oxide octahydrate
Li3N∙ 3H2O
BaS∙ 4H2O

34. Interpreting Formulas
To represent more than one formula unit of a compound- place a coefficient before the formula Example: two formula units of NaCl – 2NaCl Formulas summarize how many atoms of each element are present: Examples: (NH4)2SO4 2 N, 8H, 1S, 4O

35. Interpreting Formulas
Try this:
3Al2(CrO4)3
6 Al, 9 Cr, 36 O
5Ba3(PO4)2
15 Ba, 10 P, 40 O