1. Chemistry Lesson 8: Ions
Learning about ions and drawing Bohr Model Diagrams

2. What element is this?
Sodium
Why is it so sad?
It doesn’t have a full valence shell (only 1 electron)

3. What element is this?
Neon
Why is it so happy?
It has a full valence shell (8 electrons)

4. How could sodium become happy?
By losing that valence electron so that it has a full outer shell.

5. When Sodium loses that electron it is no longer considered an atom.
It is now an ion with a 1+ charge.

6. Sodium Ion Neon atom
Notice the similarities between the sodium (Na) ion and the neon (Ne) atom

7. Noble Gas Stability
Since all of the noble gases have full valence shells we refer to them as “stable”.
The fact that their outer shells are full means they are quite happy and don't need to react with other elements.
Other elements without full valence shells want to achieve noble gas stability.

8. Noble Gas Stability
• Atoms try to get to the level of stability of noble gases by gaining or losing electrons.

9. metal ions vs. non-metal ions
Metals will often lose their valence electrons to be left with a full valence shell. Atoms of metals lose e- to form positive ions (cations).
Non-metals will gain electrons to fill their valence shell. Atoms of non- metals gain e- to form negative ions (anions).

10. Superscripts show the ions they form
Ion charge shown on the symbol by a superscript number followed by a + or - sign. The number is equal to the sum of charges of its protons and electrons.
Example: the magnesium ion has 12 protons and 10 electrons
= +2
Example: the sulphur ion has 16 protons and 18 electrons
= -2

11. ..so in conclusion
An ion is an atom that has gained or lost electrons.
In non-nuclear chemistry an atom never gains or loses a proton; only the number of electrons is affected during chemical reactions.
Most elements have their ionic charges shown on the periodic table which reveals the ion that they form (some even have more than one charge!)

12. Rules for drawing Bohr Model diagrams for ions
Find your element on the periodic table.
Draw the nucleus the same way you would for an atom.
Determine the number of electrons the ion would have based on it’s ionic charge.
Place the electrons on the proper shells (2, 8, 8, 18)
Use square brackets to indicate an ion along with the ion charge.