1. Writing Polyatomic Compounds

2. Polyatomic Compounds Not all compounds are Binary
Polyatomic Compounds have more than two elements in a compound.
Poly = many

3. Example: How many elements are in this compound?
K2(SO4) Potassium Sulfate
How many elements are in this compound? 3

4. Polyatomic Ions
A Polyatomic Ion is a positively or negatively charged group of covalently bonded atoms.
Examples:
Sulfate (SO4)-2
Hydroxide (OH)-
Sulfite (SO3)-2
Ammonium (NH4)+

5. Writing Polyatomic Compounds
Polyatomic compounds use the same rules as binary except the polyatomic ion has a parentheses around the group when there is more than one ion.

6. Rules for Writing Ionic Compounds
K+ + (SO4)-2 = K
(SO4) 2
Write the symbol of the element with the positive oxidation number.
Write the symbol of the element with the negative oxidation number. (Put parentheses around the polyatomic groups)
Cross and drop the oxidation numbers without the charge
If both subscripts are divisible by the same number, they must be reduced

7. Examples: Sr+2 + (OH)- = K+ + (PO4)-3 = Li+ + (SO4)-2 =
Sr(OH)2 Strontium Hydroxide
K3(PO4) Potassium Phosphate
Li2(SO4) Lithium Sulfate

8. The End