Chapter 1: 1.2 Lewis Structures and Formal Charges

Question 1

Explain:

Lewis structures

Answer 1

Allows us to see how electrons are arranged around an atom(s)
* Shows bonding pairs of electrons and lone pairs of electrons
* Lets us determine the molecular shape and geometry

Question 2

What are Lewis structures also known as?

Answer 2

Lewis dot diagrams

Question 3

Explain:

Formal charges

Answer 3

Allows us to see the charge on an atom (either neutral, positive, or negative) in a Lewis structure

Question 4

Each atom will have a charge, that will be dictated by…

Answer 4

The number of bonds or lone pairs

Question 5

How is formal charge calculated?

Answer 5

Formal Charge = Valence e - (lone pair e + number of bonds)

Question 6

Describe:

How to draw Lewis Structure

(5 steps)

Answer 6

1. Position most electropositive atom in the middle with more electronegative atoms around it
2. Add valence electrons and form bonds between the central and terminal atoms
3. If necessary, complete the octets of the terminal atoms by moving electrons out from the central atom
4. Calculate formal charges and add double bonds if necessary
5. Check to make sure all atoms that should follow the octet rule have complete octets

Question 7

In Lewis structures:

When adding valence electrons, what should we be aware of?

Answer 7

Overall molecule charge

Question 8

State:

The number of electrons for the following:
1. 1 bond
2. 2 bonds
3. 3 bonds

Answer 8

1. 2 electrons
2. 4 electrons
3. 6 electrons

Question 9

True or False:

Some atoms may not follow the octet rule

Answer 9

True

Question 10

Give typical examples of atoms that don’t follow octet rule

Answer 10

• Hydrogen: Makes one bond
• Boron: Makes three bonds
• Phosphorus: Makes five bonds
• Sulfur: Makes six bonds

Question 11

True or False:

Carbon doesn’t follow the octet rule

Answer 11

False, Carbon and nitrogen can form a maximum of 4 bonds