1. Ions

2. What is a chemical reaction?

3. Sodium
Sodium atom

4. Chlorine
Chlorine atom

5. A chemical reaction

6. Or…
Word equation: Sodium + Chlorine Sodium chloride Symbol equation: Na + Cl NaCl

7. It’s all in the valency
Chemicals react with one another depending on what’s going on in their outermost electron shell – the valence shell.

8. How is an ion formed?
If the valence shell does not have its full compliment of electrons, it will lose or gain electrons from another atom to make it full.
When this happens, it becomes an ion.
An ion is a charged atom or molecule. It is charged because the number of electrons do not equal the number of protons in the atom or molecule.

9. Positive or negative?
Ions will have either a positive or negative charge, depending on whether they have lost or gained electrons.
Metals tend to lose electrons to become positive ions.
Non-metals tend to gain electrons to become negative ions.
Remember, atoms have no charge as they have the same number of protons and electrons.
So…back to our sodium and chlorine atoms…

11. Task Find Magnesium and Oxygen on your periodic table.
Draw atoms of Magnesium and Oxygen.
Write their electron configuration.
Draw Magnesium and Oxygen when they have become ions.
Write the symbols for Magnesium and Oxygen ions.