1. HL Bonding Resonance Structures & Delocalisation of Electrons

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

3. 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

4. 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 0.127 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 0.127 nm, which are shorter than a single bond and longer than a double bond

5. Resonance Structures of HCOO - From: www.mpcfaculty.net/mark_bishop/resonance.htm

6. Resonance Structures  These different structures are known as resonance hybrids

7. 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

8. 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

9. 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

10. e.g. ozone From: http://academic.reed.edu/chemistry/roco/Resonance/major_minor.html

11. e.g. ozone From: http://academic.reed.edu/chemistry/roco/Resonance/major_minor.html Instead of drawing the resonance structures, a dotted/dashed line may be used to represent a partial bond.

12. e.g. CO 3 2- From: http://www.mhhe.com/physsci/chemistry/carey/student/olc/graphics/carey04oc/ch01/figures/res1.gif

13. e.g. benzene From: http://mooni.fccj.org/~ethall/benzene/benzene.htm

14. e.g. benzene From: http://mooni.fccj.org/~ethall/benzene/benzene.htm 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

15. Can you draw 3 resonance structures for NO 3 - ?

16. From: http://en.wikipedia.org/wiki/Image:Nitrate_ion_resonance_structures.png

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