HL Bonding

HL BondingHL Bonding

Resonance Structures & Delocalisation of

Electrons

Resonance Structures & Delocalisation of

Electrons

Resonance StructuresResonance 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



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

Resonance Structures of HCOO-

Resonance Structures of HCOO-

From: www.mpcfaculty.net/mark_bishop/resonance.htm


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




This process of electrons “spreading out” is called delocalisation

e.g. ozonee.g. ozone

From: http://academic.reed.edu/chemistry/roco/Resonance/major_minor.html

e.g. ozonee.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.

e.g. CO32- e.g. CO32-

From: http://www.mhhe.com/physsci/chemistry/carey/student/olc/graphics/carey04oc/ch01/figures/res1.gif

e.g. benzenee.g. benzene

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

e.g. benzenee.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 sp2 hybridized, with the remaining p electron being delocalised

Can you draw 3 resonance structures

for NO3-?


for NO3-?


for NO3-?


for NO3-?

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


for SO32-?


for SO32-?

HL Bonding

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