1. Unit 2: Chemical Nomenclature
Section 2: Polyatomic & Stock System Ions

2. Polyatomic Ions
A group of two or more elements that stay together and act as one ion
Example: NH4+
Nitrogen and Hydrogen are one ion

3. Common Polyatomic Ions
NH4+  Ammonium
NO2-  Nitrite
NO3-  Nitrate
SO32-  Sulfite
SO42-  Sulfate
OH-  Hydroxide
PO33-  Phosphite
PO43-  Phosphate
CO32-  Carbonate

4. Naming Polyatomic Ions
General way binary compounds are named
Use the name of the polyatomic ion
In most cases, parentheses are needed around polyatomic ions

5. Examples of Polyatomic Compounds
Sodium and Nitrate
Formula: Na+ and NO3-  NaNO3
Because there are 1+ and 1-, nothing else needs to be done
Name: Sodium Nitrate

6. Examples of Polyatomic Compounds
Calcium and Nitrate
Formula: Ca2+ and NO3-  Ca(NO3)2
The parentheses shows that the entire nitrate ion gets doubled
Name: Calcium Nitrate

7. Let’s practice!!!

8. Stock System Ions Ion that can have more than one charge
Example: Fe2+ and Fe3+
Most transition metals are stock system ions

9. Naming Stock System Ions
Same method as naming Polyatomic compounds
Roman numerals are used to specify the charge
1  I
2  II
3  III
4  IV
- 5  V

10. Examples of Stock System Compounds
Tin and Chlorine
Formula 1: Sn2+ and Cl-  SnCl2
Name 1: Tin (II) Chloride
Formula 2: Sn4+ and Cl-  SnCl4
Name 2: Tin (IV) Chloride

11. Examples of Stock System Compounds
Copper and Nitrate
Formula 1: Cu+ and NO3-  CuNO3
Name 1: Copper (I) Nitrate
Formula 2: Cu2+ and NO3-  Cu(NO3)2
Name 2: Copper (II) Nitrate

12. Let’s practice!!!