1. Compound Names and Formulas
Ch 5.2 and 5.3

2. Polyatomic Ions “Poly” means many, and “Atomic” means atom, so…
Polyatomic ions are ions made of two or more atoms
Examples:
Hydrogen Carbonate, HCO3-
Hydroxide Ion, OH-
Ammonium Ion, HN4+

3. Polyatomic Ions The charge applies to the whole polyatomic ion
Example: Nitrite Ion, NO2-
The negative charge applies to the oxygen and to the nitrogen

4. Naming Ionic Compounds
Ionic compounds formed between positive ions (cations) and negative ions (anions)
Naming anions (negative ions):
Keep the same beginning, and change the ending
Examples:
Fluorine, F  Fluoride Ion, F-
Chlorine, Cl  Chloride Ion, Cl-
Oxygen, O  Oxide Ion, O-2
Nitrogen, N  Nitride Ion, N-3

5. Naming Ionic Compounds
Keep the cation (positive ion) the same, and change the anion (negative ion) to its altered state (seen on previous slide)
Examples:
NaF
Made from Na+ and F-
Cation, Sodium Na+ Keep the same
Anion, Fluorine F- Change to Fluoride
Write the cation first, always
Therefore, the name is sodium fluoride

6. So how do you name this? FeO vs. Fe2O3
Cannot just say iron oxide—have to be more specific
To specify, we look at the charge of the cation (positive ion/the metal/the first atom)
Transition metals can have different charges depending on what they are bonded to

7. Naming Ionic Compounds
FeO
Fe is a transition metal and the charge can vary
Therefore start with O and figure out its charge
Oxygen is group 16, therefore forms -2 charges
Therefore Fe must have +2 charges to balance out the oxygen
Write the charge of the cation (Iron, +2) in parentheses after the metal, Iron (II)
Name of FeO: Iron (II) Oxide

8. How do you name… Fe2O3 What is the charge of one oxygen ion?-2
There are three oxygen atoms, therefore oxygen has an overall charge of (-2)(3) = -6
Therefore iron must contribute a +6 charge to balance out the oxygen
There are two iron atoms, so each atom must have a +3 charge because (2)(+3) = +6
Since iron has a charge of +3, the name of Fe2O3 is iron (III) oxide

9. Writing formulas… What is the chemical formula for aluminum fluoride?
Use Table 4 (Page 159)Charge of an aluminum ion is +3
Use Table 5 (Page 160)Charge of a fluoride ion is -1
Step 1: Write down ions beside each other, with the cation first
Al+3F-

10. Writing ionic formulas…
What is the chemical formula for aluminum fluoride?
Al+3F-
Trick! Cross the charges to get the amount of ions in each.
Becomes AlF3

11. Let’s see it another way…

12. Practice… Write lithium oxide Li+1 O-2
Write the cation first: Li+1 O-2
Cross the charges
Therefore lithium oxide is Li2O

13. Practice Write beryllium chloride Be+2 Cl-1 Write cation first.
Cross the charges.
So beryllium chloride is BeCl2

14. Practice Write titanium (III) nitride
Remember: (III) corresponds to charge
So Ti+3
Nitride-3
Write the cation first.
If you cross the charges, you get Ti3N3 which can be reduced to a ratio of 1:1
So titanium (III) nitride is TiN

15. Challenge Practice Write cobalt (III) hydroxide Co+3
Hydroxide ion, OH-
Write the anion first, then cross the charges!
Co(OH)3
Remember to keep OH is parentheses since it is one polyatomic ion!