1. Binary Compounds
When two elements meet

2. Almost all elements hold some kind of charge You need to know these!+1 +2 -3 -2 -1

4. How to Write a Chemical Formula
Find the charges of each element from their placement on the periodic table.
Write the chemicals with their charges next to each other.
Take the charge of the first element and make it the subscript of the second, and take the charge of the second element and make it the subscript of the first. (Ignore negative and positive in this step!)
If the new subscripts have a common multiple, divide by that multiple.

5. Writing a Formula Example
Write the formula for the ionic compound that will form between Ba and Cl.
Find the charges of each element from their placement on the periodic table.
Ba has a +2 charge and Cl has a -1 charge
2. Write the chemicals with their charges next to each other.
Ba2+ Cl1-
3. Take the charge of the first element and make it the subscript of the second, and take the charge of the second element and make it the subscript of the first. (Ignore negative and positive in this step!)
Ba2+ Cl1-  𝐵𝑎 𝐶𝑙 2 1−
4. If the new subscripts have a common multiple, divide by that multiple.
Final formula: BaCl2

6. Do these examples
Na, S
Al, Cl
Mg, N

7. Solution
Na, S  Na2S
Al, Cl  AlCl3
Mg, N  Mg3N2

8. Naming Compounds
Binary Ionic Compounds 1. Cation first, then anion 2. Monatomic cation = name of element ex: Ca2+ = calcium 3. Monatomic anion = root + -ide ex: Cl1- = chloride CaCl2 = calcium chloride

9. Do these Examples
NaCl
ZnI2
Al2O3

10. NaCl  Sodium Chloride ZnI2  Zinc Iodide Al2O3  Aluminum Oxide
Solution
NaCl  Sodium Chloride
ZnI2  Zinc Iodide
Al2O3  Aluminum Oxide

11. Transition Metals **A Special Case**
Transition metals can have more than one possible charge, and MUST have a Roman Numeral to indicate the charge on the individual ion
1+ or or 3+
Cu+, Cu Fe2+, Fe3+
copper(I) ion iron(II) ion
copper (II) ion iron(III) ion

12. How do I know which elements need a roman numeral?
ANY METAL EXCEPT GROUPS 1A, 2A, Ag, Zn, Cd, and Al
(You should know the charges of these elements already!)
Examples:
FeCl3 (Fe3+) iron (III) chloride
CuCl (Cu+ ) copper (I) chloride
SnF (Sn4+) tin (IV) fluoride
PbCl (Pb2+) lead (II) chloride
Fe2S (Fe3+) iron (III) sulfide

13. Learning Check
Complete the names of the following binary compounds with variable metal ions: FeBr2 iron (_____) bromide CuCl copper (_____) chloride SnO2 ___(_____ ) ______________ Fe2O3 ________________________ Hg2S ________________________

14. Solution
Complete the names of the following binary compounds with variable metal ions: FeBr2 iron (II) bromide CuCl copper (I) chloride SnO2 tin (IV) oxide Fe2O3 iron (III) oxide Hg2S mercury (I) sufide