Resonance

Question 1

What is resonance?

Answer 1

Movement of non-skeletal electrons over skeletal arrangements of atoms (delocalization)

Question 2

What are resonance forms?

Answer 2

Two or more lewis diagrams for the same arrangement of atoms (same skeleton, same number of valence electrons), where some of the non-skeletal electrons are delocalized and arranged differently
- Move lone pair from an atom to a bond
- Move electrons from a multiple bond to an atom

Question 3

What are the rules for resonance forms?

Answer 3

• Single bonds in the original skeleton cannot be broken
• Nuclei do not change position
• Second row elements cannot have more than an octet

Question 4

What is a resonance hybrid?

Answer 4

When there are two or more most significant lewis diagrams that are equivalent, one can consider the average (resonance hybrid), with delocalized electrons being distributed over the whole species

Question 5

Is hybrid resonance a lewis diagram?

Answer 5

No.

Question 6

What happens if there are charges on the two equivalent resonance forms and a resonance hybrid is to be made?

Answer 6

The charge will be divided based on how many atoms have that charge

Question 7

What do dashed lines represent in a resonance hybrid?

Answer 7

Electron delocalization

Question 8

What does the resonance arrow look like?

Answer 8

Straight line with two arrows at each end

Question 9

What are the two components of hybrid resonance?

Answer 9

1. Static (things not changing)
2. Dynamic (things that are moving)
   - Like lone pairs and electrons in double bonds

Question 10

What molecule can we not draw a resonance hybrid for?

Answer 10

CO2 because there is only one “most significant” lewis diagram that has the largest contribution to resonance/delocalization. The other resonance forms are too unstable. For this molecule, we consider the electrons localized

Question 11

What do you show when you have non-equivalent resonance forms?

Answer 11

The most significant lewis diagram