10.8 Resonance and Formal Charge

resonance structure

two or more valid Lewis structures that are shown with double-headed arrows between them to indicate that the actual structure of the molecule is intermediate between them

true

(true/false) Individual resonance structures do not actually exist and are merely a way to describe actual structure.

false

(true/false) The molecule resonates between different forms.

true

(true/false) The skeletal formula of resonance structures does not change, only electron arrangement.

resonance hybrid

the actual structure of a molecule that is intermediate between two or more resonance structures, the only structure that actually exists

decreases

The delocalization of electrons over several atoms or bonds in nature stabilizes them and __________ (increases/decreases) energy.

resonance stabilization

resulting stabilization of electrons, lowering of potential energy due to delocalization

true

(true/false) Multiple nonequivalent resonance structures may be weighted differently in their contributions to true overall structure of a molecule.

formal charge

the charge that an atom in a Lewis structure would have if all the bonding electrons were shared equally between the bonded atoms, ignoring the effects of electronegativity in order to distinguish competing Lewis structures

• FC = VE - NBE - 1/2BE

FC = VE - NBE - 1/2BE

formal charge equation

true

(true/false) The sum of all formal charges in a neutral molecule must be 0.

false

(true/false) The sum of all formal charges in an ion must be 0.

better

Small (or zero) formal charges on individual atoms are ______ (better/worse) than large ones.

most

When formal charge cannot be avoided, negative formal charge should reside on the ____ (least/most) electronegative atom.

positive

Since atoms in the middle of a molecule tend to have more bonding electrons and fewer nonbonding electrons, they also tend to have more ________ (positive/negative) formal charges.

least

The best skeletal structure usually has the ______ (least/most) electronegative atom in the central position.