1. Writing Ionic Compounds
The “Swap & Drop” Method

2. Why do atoms form ions? All atoms want to gain stability.
We need to look at the valence electrons of each atom.
Valence Electrons: Electrons in the outermost energy level.
All atoms want to get to eight valence electrons to become stable.
“8 is Great!!!”

3. K Cl - + 1 1 Swap & Drop Method For Ionic Compounds Only!
Potassium Ion K
Chlorine Ion Cl - + 1 1
Step 1: Drop the signs.

4. K Cl 1 1 Swap & Drop Method Step 2: Swap Values. Potassium Ion
Chlorine Ion Cl 1 1
Step 2: Swap Values.

5. K Cl 1 1 1 1 Swap & Drop Method Step 3: Drop Values to Subscripts.
Potassium Ion K
Chlorine Ion Cl 1 1 1 1
Step 3: Drop Values to Subscripts.

6. Swap & Drop Method
Potassium Ion K
Chlorine Ion Cl
Potassium Chloride
Step 4: When the values are the same, then they can be erased. The number (1) is never required.

7. Al O - + 3 2 Swap & Drop Method Step 1: Drop the signs. Aluminum Ion
Oxygen Ion O - + 3 2
Step 1: Drop the signs.

8. Al O 3 2 Swap & Drop Method Step 2: Swap Values. Aluminum Ion
Oxygen Ion O 3 2
Step 2: Swap Values.

9. Al O 2 3 2 3 Swap & Drop Method Step 3: Drop values to subscripts.
Aluminum Ion Al
Oxygen Ion O 2 3 2 3
Step 3: Drop values to subscripts.

10. Al O 2 3 Swap & Drop Method Step 4: Combine into compound.
Aluminum Ion Al
Oxygen Ion O 2 3
Aluminum Oxide
Step 4: Combine into compound.