1. Lewis Dots & Ionic Bonding
Due Thursday 11/14/13

2. Objectives
Draw Lewis Dot Diagrams to represent the number of valence electrons an atom has
Write the chemical formula for ionic compounds using the criss-cross method and the Lewis Dot method
**Show all work for all problems!

3. Lewis Dot Diagrams AKA Electron Dot Diagrams Consists of
Element symbol in the center
1-8 dots around the symbol representing valence electrons
Lewis dot diagrams are also known as electron dot diagrams and are used to represent the number of valence electrons an atom has. A Lewis Dot Diagram is created by writing the symbol of the element in the center and then placing 1 to 8 dots around the symbol to represent the number of valence electrons.

4. Lewis Dot Diagrams Steps: 1. Write the element’s symbol
2. Find the group #1A-8A. The group #1A-8A = Valence Electrons = Lewis Dots
3. Put a Lewis dot on each side of the element first before doubling up
To create a Lewis Dot Diagram you first write the element’s symbol, the first letter is capitalized and the second letter is lower case. Then find the group that the element belongs to. The group number, 1A through 8A, equals the number of valence electrons the atom has, and thus the number of Lewis dots. You then place a Lewis dot on each side of the element first before going back and doubling up. A Lewis dot by itself shows an electron that is available for bonding, whereas paired electrons are not available for bonding.

5. Lewis Dot Diagrams Examples: Sodium Carbon Chlorine

6. Ionic Bonds Metal & nonmetal - Metals lose electrons and form cations
- Nonmetals gain electrons and form anions
- This electrostatic attraction holds the atoms in an ionic bond together
As a reminder, an ionic bond is formed between a metal and a nonmetal. The metals will lose electrons to form positively charged cations, and the nonmetals will gain electrons to form negatively charges anions. The electrostatic attraction between the positively charged cation and the negatively charged anion holds the atoms in the ionic bond together.

7. Ionic Bonds – Criss Cross
Steps:
1. Find the common charge for each atom
2. The charge on the metal becomes the subscript for the nonmetal
3. The charge on the nonmetal becomes the subscript for the metal
- Overall net charge is 0
- Metal is written first in the formula
There are two ways to derive the formula for an ionic compound. To review from class, one method is the criss-cross method. In the criss-cross method you first find the common charge for each atom. Then the charge on the metal crosses down to become the subscript for the nonmetal, and the charge on the nonmetal crosses down to become the subscript for the metal. In doing so, the overall net charge is 0. As a reminder, the metal is always written first in the formula for an ionic compound.

8. Ionic Bonds – Lewis Dots
Steps:
1. Draw the Lewis Dot Diagram for the metal
2. Draw the Lewis Dot Diagram for the nonmetal
3. Transfer one electron at a time from the metal to an available spot on the nonmetal
4. Continue until the metal has lost all of its electrons, and the nonmetal has a full octet
A second way to derive the formula for an ionic compound is the Lewis Dot method. In this method you draw the Lewis dot diagram for the metal, and the Lewis dot diagram for the nonmetal. Then you transfer each electron from the metal to an available spot on the nonmetal until the metal has lost all of its electrons and the nonmetal has a full octet. Sometimes this means that additional metal or nonmetal atoms must be drawn.

9. Ionic Bonds – Practice 1
Potassium & Chlorine
KCl

10. Ionic Bonds – Practice 2
Magnesium & Phosphorous
Mg3P2

11. Questions