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. +1 ion LOSE 1 ELECTRON! Look at Group 1!
All group 1 elements have 1 valence electron.
Is it easier for them to lose 1 electron,
or try to gain 7 electrons?
LOSE 1 ELECTRON!
+1 ion

4. +2 ion LOSE 2 ELECTRONS! Look at Group 2!
All group 2 elements have 2 valence electron.
Is it easier for them to lose 2 electrons,
or try to gain 6 electrons?
LOSE 2 ELECTRONS!
+2 ion

5. +3 ion LOSE 3 ELECTRONS! Look at Group 3!
All group 3 elements have 3 valence electron.
Is it easier for them to lose 3 electrons, or try to gain 5 electrons?
LOSE 3 ELECTRONS!
+3 ion

6. +4 ion LOSE 4 ELECTRONS! Look at Group 4!
All group 4 elements have 4 valence electron.
Because 4 is in the middle, we usually just call all Group 4 Ions +4
LOSE 4 ELECTRONS!
+4 ion

7. -3 ion GAIN 3 ELECTRONS! Look at Group 5!
All group 5 elements have 5 valence electron.
Is it easier for them to lose 5 electrons, or try to gain 3 electrons?
GAIN 3 ELECTRONS!
-3 ion

8. -2 ion GAIN 2 ELECTRONS! Look at Group 6!
All group 6 elements have 6 valence electrons.
Is it easier for them to lose 6 electrons, or try to gain 2 electrons?
GAIN 2 ELECTRONS!
-2 ion

9. -1 ion GAIN 1 ELECTRON! Look at Group 7!
All group 7 elements have 7 valence electrons.
Is it easier for them to lose 7 electrons, or try to gain 1 electron?
GAIN 1 ELECTRON!
-1 ion

10. 8 is GREAT!!! No Ions Needed!!! Look at Group 8!
All group 8 elements have 8 valence electrons.
8 is GREAT!!! No Ions Needed!!!

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

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

13. 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.

14. 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.

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

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

17. 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.

18. 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.