HL Bonding Resonance Structures & Delocalisation of Electrons

Resonance Structures  Occurs when electrons are “shared” between more than one bond

Resonance Structures  Occurs when electrons are “shared” between more than one bond  Presence can be identified from bond lengths and bond angles  Occurs when electrons are “shared” between more than one bond  Presence can be identified from bond lengths and bond angles

Resonance Structures  Occurs when electrons are “shared” between more than one bond  Presence can be identified from bond lengths and bond angles  E.g. HCOO - has C to O bond lengths of nm, which are shorter than a single bond and longer than a double bond  Occurs when electrons are “shared” between more than one bond  Presence can be identified from bond lengths and bond angles  E.g. HCOO - has C to O bond lengths of nm, which are shorter than a single bond and longer than a double bond

Resonance Structures of HCOO - From:

Resonance Structures  These different structures are known as resonance hybrids

Resonance Structures  These different structures are known as resonance hybrids  These are the extreme forms with the actual structure somewhere in between  These different structures are known as resonance hybrids  These are the extreme forms with the actual structure somewhere in between

Resonance Structures  These different structures are known as resonance hybrids  These are the extreme forms with the actual structure somewhere in between  A double-headed arrow is always used to show resonance structures  These different structures are known as resonance hybrids  These are the extreme forms with the actual structure somewhere in between  A double-headed arrow is always used to show resonance structures

Resonance Structures  These different structures are known as resonance hybrids  These are the extreme forms with the actual structure somewhere in between  A double-headed arrow is always used to show resonance structures  This process of electrons “spreading out” is called delocalisation  These different structures are known as resonance hybrids  These are the extreme forms with the actual structure somewhere in between  A double-headed arrow is always used to show resonance structures  This process of electrons “spreading out” is called delocalisation

e.g. ozone From:

e.g. ozone From: Instead of drawing the resonance structures, a dotted/dashed line may be used to represent a partial bond.

e.g. CO 3 2- From:

e.g. benzene From:

e.g. benzene From: As the C-C-H bond angles in benzene are 120 °, the carbon atoms are sp 2 hybridized, with the remaining p electron being delocalised

Can you draw 3 resonance structures for NO 3 - ?

From:

Can you draw 3 resonance structures for SO 3 2- ?