1. POLYATOMIC IONS

2. Poly - many
Atomic - atoms
Polyatomic ion - a many atom ion
- a group of atoms tightly held together that acts like a single ion
All are negative except for NH4+ (ammonium), the only positive polyatomic ion

3. Writing Names The metal is written as before:
If a single valent metal, just write the name
If it is a multivalent metal, you must include the roman numeral indicating the charge.
Ammonium is single valent. If ammonium is the positive ion, do NOT use a roman numeral
A negative polyatomic ion is written as is with out change

4. EXAMPLES
KNO3
Potassium is single valent, so no roman numerals
Potassium nitrate

5. FeSO4
Iron is multi Valent, so we must find its ionic charge
Fe SO42-
Iron (II) sulphate

6. Al(ClO4)3
Aluminum perchlorate

7. Fe2(CO3)3
Iron is multivalent
Fe+3 CO32-
CO32-
___________________
Iron (III) carbonate

8. NH4Br
Ammonium Bromide
(NH4)3PO4
Ammonium phosphate

9. WRITING FORMULA Done the same as before except:
If there is more than 1 of the polyatomic ion, it MUST be in brackets
If there is only one of the polyatomic ion, it MUST NOT be in brackets
DO NOT CHANGE THE FORMULA

10. EXAMPLES
Barium sulphite
Ba SO32-
Just need one of each
BaSO3

11. Ammonium carbonate
NH CO32-
NH4+
______________________
(NH4)2CO3

12. Lead ( II ) hydroxide
Pb OH-
OH-
__________________
Pb(OH)2

13. Cobalt (II) phosphate
Co PO43-
Co PO43-
Co+2
___________________
Co3(PO4)2