WRITING IONIC FORMULAS. Write the symbol for the cation, then the symbol for the anion. Balance the charges - use the crisscross method - by placing subscripts and “( )” for polyatomic ions if needed. Monatomic ions don’t need “( )”.
Ex. Aluminum chloride. Al and Cl.
Al3+ Cl1- Al3 Cl1 Don’t need to record “1”s
+3 -1 -1 -1 = 0
Cations can have more than one oxidation number.
Example: Cu+1 and Cu+2.
It is important to distinguish which ion is in the compound.
There are two ways used in chemistry.
Stock SystemClassical (Latin)
Cu+1 copper (I)cuprous
Cu+2 copper (II)cupric
Sn+4 tin (IV)stannic
Hg2+2 mercury (I)mercurous
Hg+2 mercury (II)mercuric
The lower charge ends in –ous and the higher charge ends in –ic.
You are only responsible for only the Stock system but I just wanted you to see the other.
You are only responsible in class for the Stock system but I wanted to make you familiar with the classic.
cupric sulfate/copper (II) sulfateCuSO4
ferrous oxide/iron (II) oxide
cobaltic chloride/cobalt (III) chloride
mercurous nitrate/mercury (I) nitrate
You need to make sure that you can distinguish between ionic, covalent, and acid compounds.