1. Lewis Structures and Ions
Answer the following questions:
How do you determine the number of valence electrons for an atom?
How many valence electrons do each of the following atoms contain?
Potassium: Sulfur:
Silicon: Calcium:

2. Write the # of valence electrons and the dot diagram for each element: 1. Li S 3. Ba 4. Sn At Si Li S Ba Sn At Si 1 6 2 4 7

3. Lewis dot structures of Group 1A through 8A
I A A A A A A A A

4. Ions
Cation  Atom  Anion

5. Ion- Atom’s which either gain or lose electrons
They do this to become more stable
They become ISOELECTRONIC(iso means same) - same number of electrons as the noble gases.
This is called the OCTET RULE: atoms will gain or lose electrons to have full shells

6. Fluorine gains an electron and becomes negatively charged
F + e-  F-

7. Sodium loses an electron and becomes positively charged
Na  Na+ + e-

8. Quick Activity- Atom charges and Ions
PART I- CATION: LITHIUM:
For the atom Lithium : How many Protons and Electrons does this atom contain?
For each Proton take a + paper, for each electron take a – paper.
What charge does the atom have? 
To become isoelectronic with Helium Lithium will lose one electron. Take away one – paper.
What charge does Lithium have now?

9. Quick Activity- Atom charges and Ions
PART II- ANION: OXYGEN:
For the atom Oxygen : How many Protons and Electrons does this atom contain?
For each Proton take a + paper, for each electron take a – paper.
What charge does the atom have?
To become isoelectronic with Neon Oxygen will gain two electrons. Add two – papers.
What charge does Oxygen have now?

10. PART III- Mixed practice: Fill in the table below for each element

11. Cation
anion
Positive ion
Negative ion

12. Cation
anion
Positive ion
Negative ion
Lose their valence electrons
Gain valence electrons

13. Use your periodic table to help!

14. Cation
anion
Positive ion
Negative ion
Lose their valence electrons
Gain valence electrons
From atoms with less than 4 valence electrons
From atoms with more than 4 valence electrons

15. Mg  Mg2+ + 2e- Cl + e-  Cl- Cation Anion Positive ion Negative ion
Lose their valence electrons
Gain valence electrons
From atoms with less than 4 valence electrons
From atoms with more than 4 valence electrons
Example: Mg
Mg  Mg2+ + 2e-
Example: Cl
Cl + e-  Cl-

17. Size difference… Cation is smaller than parent element because:
Same number of protons (+)
Lesser number of energy shells.
Anion is larger than parent element because:
More electrons and more shielding by inner electrons

18. Smaller than parent element Larger than parent element
Cation
Anion
Positive ion
Negative ion
Lose their valence electrons
Gain valence electrons
From atoms with less than 4 valence electrons
From atoms with more than 4 valence electrons
Example: Mg
Mg  Mg2+ + 2e-
Example: Cl
Cl + e-  Cl-
Smaller than parent element
(less electrons, same protons)
Larger than parent element
(more electrons, same protons)

19. Ion formation