C4. Resonance

Question 1

Describe the lewis model

Answer 1

• Does not model delocalised electron behaviour
• Does not explain relative bond strengths (σ vs π)

Question 2

Describe the atomic orbital/ hybrid orbital theory

Answer 2

• Good at predicting shapes and bonding
• Explains bond strengths
• Still predicts localised bonding

Question 3

Describe the resonance theory

Answer 3

• Can be applied to Lewis model or AO model
• Predicts delocalised bonding

Question 4

What does the resonance theory state

Answer 4

This states that there can be various possible structures for a molecule, and that no individual one of them is correct, but all contribute to the “true” structure

Question 5

what is the limitation of the lewis structure

Answer 5

The Lewis structure is unable to accurately describe the structure of
the carbonate anion, and many others

Question 6

what does a resonance arrow look like?

Answer 6

double headed arrow

Question 7

curly arrow vs radical arrow?

Answer 7

curly arrow- movement of a pair of electrons
radical arrow- movement of a single electron

Question 8

are resonance structures all equal?

Answer 8

no

Question 9

How does each resonance form contribute? (which is most stable form and therefore most “true” form)

Answer 9

-structures with more covalent bonds are more stable
-structures with separation charge are less stable
-structures where a negative charge is on an electronegative atom are more stable than those where it is on a electropositive atom