1. Properties, Writing Chemical Formulas & Naming Ionic Compounds

2. Ionic Compounds Compounds that are composed of cations and anions
Binary Compound- compound composed of 2 elements
Electrically Neutral
Na 1+ +Cl1-  NaCl

3. Chemical Formula vs. Formula Unit
Chemical Formula- shows different kinds of numbers of atoms in a small representative unit. Ex: H2O
Formula Unit- lowest whole # ratio of ions in an ionic compound
Ex: Na 1+ +Cl1-  NaCl; ratio 1:1
Ex: Mg 2+ +Cl1-  MgCl2 ; ratio 1:2

4. Properties Most are crystalline solids at room temperature
Arranged in repeating 3 dimensional pattern
Generally have high melting points
Can conduct electric current when melted or dissolved in H2O
salts

5. Writing Formulas for Ionic Compounds
1. Write the symbol of the cation first
2. Then write the symbol of the anion.
3. Add subscripts to balance charge
Positive charge= negative charge

6. Examples 1. Potassium Chloride K 1+ Cl 1- 1 valence e’s 7 valence e’s
lose 1 or lose 7 or
gain gain 1
Answer: KCl

7. #2 Calcium Bromide Ca Br 2 valence e’s 7 valence e’s
lose 2 or lose 7 or
gain gain 1
Use Criss-cross method- numerical value of ion is crossed over and becomes subscript for other ion. Signs/Charges are dropped!
Answer: CaBr2

8. #3 Iron (III) oxide Fe 3+ O2- Use the criss-cross method!
Answer: Fe2O3

9. Now you try!
Write the formulas for compounds formed from these pairs of ions
1. Ba 2+ , S2-
2. Ca 2+ , N3-
3. Li+ , O2-
4. Cu 2+ , I-
5. Sodium Iodide
6. Potassium Sulfide
7. Calcium Iodide
8. Aluminum Phosphide

10. Compounds with Polyatomic Ions
Polyatomic ions- (not binary) have more than 2 ions, normally ends in –ate or –ite
Writing Formulas with Polyatomic Ions
Write symbol for cation followed by formula for polyatomic ion.
2. Balance the charges.

11. Example #1 Pearl + Oyster shell is made of calcium carbonate
Ca CO32-
Use Criss-cross method!
Answer: CaCO3

12. Example #2 Calcium Nitrate Ca 2+ NO3- Use criss-cross method
Answer: Ca(NO3)2

13. Example #3
Lead (II) sulfate is an important component in automobile batteries.
Pb SO42-
Use Criss-Cross method!
Answer: PbSO4

14. Example #4 Ammonium Sulfate is used to make common fertilizers.
NH SO42-
Use Criss-Cross Method!
Answer: (NH4)2SO4

15. Naming Binary Ionic Compounds
Place cation name first
Next, name anion name [normally ends in –ide
Naming Compounds with Polyatomic Ions
Place cation name first.
Look up on chart polyatomic anion name.
*Exception to Rules: If cation is a transition metal, you must include its charge by writing it in Roman Numerals!

16. Examples Lithium iodide Li 1+ I 1- Answer: LiI Silver Carbonate
Ag 1+ CO32-
Answer: Ag2CO3

17. Examples Cu2O First show each ion and charge Cu 1+ O 2-
Notice: when you criss-crossed those charges, what happened?
Answer: Copper (I) oxide

18. Fe2O3
This means that Fe 3+ and O2- charge
Answer: iron (III) oxide