1. Valence Electrons & Bohr Diagrams

2. Atomic Structure
Atoms have a nucleus that contains Protons and Neutrons
Electrons are contained in shells that surround the nucleus
An atom is made of mostly empty space
Protons have a positive charge
Electrons have a negative charge
Neutrons are Neutral

3. Valence Electrons Electron Shell Number of Electrons 1 2 8 3 4 18 5 6
Each electron shell can hold a certain number of electrons
Electron shells are filled from the inside out
Noble Gases have full outer electron shells
All other elements have partially filled outer electron shells
Electron Shell
Number of Electrons 1 2 8 3 4 18 5 6 32 7

4. Valence Electrons
The electrons in the outer most electron shell are called valence electrons
The shell containing electrons that is furthest from the nucleus is called the valence shell
The number of electron shells with electrons is the same as the period number

5. Noble Gas Stability Noble gases are usually unreactive
This is because they have full valence shells
An element with a full valence shell is a happy element 
For two atoms to join together atoms must gain, lose or share electrons
Elements with full valence shells do not easily gain or lose electrons

6. Noble Gas Stability Atoms want to gain stability
Atoms will try to gain or lose electrons to have a full valence shell
Metals try to lose electrons
Non-Metals try to gain electrons

7. Becoming An Ion Electrons are negatively charged
Protons are positively charged
Neutral atoms do not have a charge because the number of protons is the same as the number of electrons
When atoms gain or lose electrons they become positively or negatively charged
An atom with a charge is called an Ion

8. IONS
IONS are atoms or groups of atoms with a positive or negative charge.
Taking away an electron from an atom gives a CATION with a positive charge
Adding an electron to an atom gives an ANION with a negative charge.
To tell the difference between an atom and an ion, look to see if there is a charge in the superscript! Examples: Na+ Ca+2 I- O-2
Na Ca I O

9. Forming Cations & Anions
A CATION forms when an atom loses one or more electrons.
An ANION forms when an atom gains one or more electrons
F + e- --> F-
Mg --> Mg e-

10. PREDICTING ION CHARGES
In general
metals (Mg) lose electrons ---> cations
nonmetals (F) gain electrons ---> anions

11. Learning Check – Counting
State the number of protons, neutrons, and electrons in each of these ions.
39 K O Ca +2
#p+ ______ ______ _______
#no ______ ______ _______
#e- ______ ______ _______

12. Charges on Common Ions -3 -2 -1 +1 +2
By losing or gaining e-, atom has same number of e-’s as nearest Group 8A atom.

13. Periodic Table Study Guide
How to Draw Lewis Structures

14. Lewis Structures Find your element on the periodic table.
Determine the number of valence electrons.
This is how many electrons you will draw.

15. Lewis Structures Find out which group (column) your element is in.
This will tell you the number of valence electrons your element has.
You will only draw the valence electrons.

16. Groups - Review Group 8 = 8 electrons Group 1 = 1 electron
Except for He, it has 2 electrons
Group 2 = 2 electrons
Each column is called a “group”
3, 4, 5, 6, 7
Each element in a group has the same number of electrons in their outer orbital, also known as “shells”.
The electrons in the outer shell are called “valence electrons”

17. C Lewis Structures Write the element symbol.
Carbon is in the 4th group, so it has 4 valence electrons.
Starting at the right, draw 4 electrons, or dots, counter-clockwise around the element symbol. C

18. C Lewis Structures Check your work.
Using your periodic table, check that Carbon is in the 4th group.
You should have 4 total electrons, or dots, drawn in for Carbon. C

19. C Lewis Structures On your worksheet, try these elements on your own:P Ca Ar Cl Al C

20. H Lewis Structures On your worksheet, try these elements on your own:P Ca Ar Cl Al H

21. P Lewis Structures On your worksheet, try these elements on your own:Ca Ar Cl Al P

22. Ca Lewis Structures On your worksheet, try these elements on your own:P Ca Ar Cl Al Ca

23. Ar Lewis Structures On your worksheet, try these elements on your own:P Ca Ar Cl Al Ar

24. Cl Lewis Structures On your worksheet, try these elements on your own:P Ca Ar Cl Al Cl

25. Al Lewis Structures On your worksheet, try these elements on your own:P Ca Ar Cl Al Al

26. End of Study Guide.
Complete the Lewis Structure Worksheet You should know how to draw Lewis Structures for the first 20 elements.