1. Forming Ions

2. Why do Ions form?
All elements want to be like their closest noble gas and have 8 electrons in their last energy level
Some elements have to lose electrons while others gain electrons to get this “stable state”

3. Positively Charged Ions (Cations)
When an atom loses an electron, you get a POSITIVELY charged ion
Cations are usually metals (less than 4 electrons in their outer shell)
Examples: Na+, Mg 2+, Al 3+

4. Negatively Charged Ions (Anions)
When an atom gains an electron, you get a NEGATIVELY charged ion.
Anions are usually non-metals ( 4 or more than 4 electrons in their outer shell)
Examples: O2-, F-, N3-

5. Calculating Charge (copy into notes)
Each proton has a charge of +1, each electron has a charge of -1
Sulfur has 16 electrons (6 valence electrons)
To reach a stable state, it wants 8 valence electrons
It gains TWO electrons, it now has 18e- (8 valence e)
Therefore, these have a charge of -18 (18 x -1)
It also has 16 p+
therefore, these have a charge of +16 (16 x +1)
Total Charge = (+16) = -2

6. Drawing an Ion Bohr Rutherford Diagram
Determine the charge and how many electrons are gained or lost
Draw a Bohr Rutherford diagram
Make sure to draw the diagram with electrons gained or electrons lost to form an ion
Put a big square bracket around the diagram
Write the ion charge on the top right of the square brackets

7. Practice by drawing a Ion Bohr Rutherford Diagram for Sulfur
Check your answer on the next slide

8. Describing an Ion Sulfur has a charge of -2, therefore we write:
Ion Notation: S-2
Ion Bohr Rutherford Diagram: -2
16p+
16n0

9. Chemical Bond
An attraction between two or more elements that allow the formation of a new substance
Only the valence electrons are involved in creating a chemical bond

10. Forming Ionic Compounds
Videos – Dogs and ions

11. Ionic Bonds
Between a metal and a non-metal
Electrons are transferred from the metal to the non-metal
From the video, why are the metal and non-metal attracted?

12. Creating an Ionic Formula
Determine the charge on the metal and the non-metal
Write them on the top right of each substance (the metal should always be written first)
Use the cross-over method to create the chemical formula
If there is a common multiple, divide each subscript by the common multiple to simplify

13. Example
Pick a metal and a non-metal

14. Naming an Ionic Compound
Write the name of the metal
Write the name of the non-metal only replace the ending with ‘ide’
Oxygen becomes Oxide
Sulphur becomes Sulphide

15. Practice!

16. Multivalent Ions A multivalent ion can have several charges
Look at the back of your periodic table
Most of these are transition metals
Iron has 2 possible charges - +2, +3
Which one should we use?
We use roman numerals to let people know which one was used. Ex: Iron (II) Oxide or Iron (III) Oxide

17. To determine which charge
Reverse Criss Cross
Cu Br2
Cu2 Br1
Since the charge on Bromine is -1, the charge on copper must be +2
Therefore, Copper (II) Bromide

18. Polyatomic Ions
Polyatomic ions are chemical best friends that are bonded together and go looking for electrons
We treat each polyatomic ion, the same way we would treat a regular ion
Still use criss cross method but they have their own special names (see back of periodic table)