3.9 resonance

Question 1

what is resonance?

Answer 1

the condition in which more than one valid lewis structure can be written for a specific model.

Question 2

formal charge is…

Answer 2

used to estimate the charge on all possible non-equivalent lewis structures. it’s defined as the difference btwn the number of valence electrons on the free atom and the number of electrons assigned to the atom in the molecule

Question 3

what is the equation for formal charge?

Answer 3

(number of valence electrons on a free atom)-(number of valence electrons assigned to the atom in the molecule)

Question 4

effects in lewis structure determination

Answer 4

atoms in molecules try to achieve charges as close to zero as possible. any negative formal charges are expected to reside on the most electronegative atoms

Question 5

what are the rules governing formal charge?

Answer 5

to calculate the formal charge of an atom:
1. take the sum of the lone pair and one half of the shared electrons
2. subtract the number of assigned electrons from the number of valence electrons on the free neutral atom.
3. the sum of formal charges of all atoms in a given molecule or ion must equal the overall charge on that species.
4. if non equivalent lewis structures exist for a species, those with formal charges closest to zero and with any negative formal charges on the most electronegative atoms are considered to best describe the bonding in the molecule or ion.