1. Ionic Compound
A compound made up of one or more positive metal ions (cations) and one or more negative non-metal ions (anions)
Most ionic compounds have:
High melting points
are hard and brittle
Form electrolytes (conduct electricity) when dissolved in water to form solutions

2. Formation of Sodium Chloride

3. Chemical Formula of an Ionic Compound
Step 1: Write the symbols of the elements, with the metal on the left-hand side and the non-metal on the right-hand side.
Mg Cl
Step 2: Add the ionic charge of each ion above the symbol
+2 -1

4. Step 3: Determine the number of ions required to bring the charge to zero.
1(+2) + 2(-1) = 0
Mg O
Step 4: Write the chemical formula using the (red) coefficients in front of each bracket as subscripts
Mg1Cl2 Note: Do not write the subscript “1”
The chemical formula for magnesium chloride is MgCl2

5. Crisscross Method
Step 1: Write the symbols of the elements and their ionic charges
Mg 2+ Cl-
Step 2: Crisscross the numbers of the ionic charges so that they now become subscripts
MgCl2

6. Considering Multiple Ionic Charges
Write the chemical name of CuBr2. Note that copper could have either of two ionic charges (+1 or +2).
Each bromide ion has a charge of -1, so the total charge of bromide ions is 2(-1).
The ionic charge of copper in this compound is +2
Roman numerals are included ONLY if the metal has more than one ionic charge.
The name of CuBr2 is copper (II) bromide