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## PowerPoint Slideshow about 'Bonding in Methane and Orbital Hybridization' - adamdaniel

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Structure of Methane

tetrahedral

bond angles = 109.5°

bond distances = 110 pm

but structure seems inconsistent withelectron configuration of carbon

Electron configuration of carbon

only two unpaired electrons

should form sbonds to only two hydrogen atoms

bonds should be at right angles to one another

2p

2s

sp3 Orbital Hybridization

4 equivalent half-filled orbitals are consistent with four bonds and tetrahedral geometry

2p

2 sp3

2s

Shape of sp3 hybrid orbitals

reinforcement of electron wave in regions where sign is the same

destructive interference in regions of opposite sign

s + p

+

–

Shape of sp3 hybrid orbitals

orbital shown is sp hybrid

analogous procedure using three s orbitals and one p orbital gives sp3 hybrid

shape of sp3 hybrid is similar

sp hybrid

+

–

Shape of sp3 hybrid orbitalshybrid orbital is not symmetrical

higher probability of finding an electron on one side of the nucleus than the other

leads to stronger bonds

sp hybrid

–

–

The C—H s Bond in Methane

In-phase overlap of a half-filled 1s orbital of hydrogen with a half-filled sp3 hybrid orbital of carbon:

+

sp3

s

H

C

gives a s bond.

+

H—C s

C

H

Justification for Orbital Hybridization

consistent with structure of methane

allows for formation of 4 bonds rather than 2

bonds involving sp3 hybrid orbitals are stronger than those involving s-s overlap or p-p overlap

tetrahedral geometry at each carbon

C—H bond distance = 110 pm

C—C bond distance = 153 pm

C2H6

CH3CH3

In-phase overlap of half-filled sp3 hybridorbital of one carbon with half-filled sp3hybrid orbital of another.

Overlap is along internuclear axis to give a s bond.

In-phase overlap of half-filled sp3 hybridorbital of one carbon with half-filled sp3hybrid orbital of another.

Overlap is along internuclear axis to give a s bond.

Structure of Ethylene

C2H4

H2C=CH2

planar

bond angles: close to 120°

bond distances: C—H = 110 pm C=C = 134 pm

sp2 Orbital Hybridization

Mix together (hybridize) the 2s orbital and two of the three 2p orbitals

2p

2s

sp2 Orbital Hybridization

3 equivalent half-filled sp2 hybrid orbitals plus 1 p orbital left unhybridized

2p

2 sp2

2s

sp2 Orbital Hybridization

p

2 of the 3 sp2 orbitalsare involved in s bondsto hydrogens; the otheris involved in a s bondto carbon

2 sp2

p Bonding in Ethylene

the unhybridized p orbital of carbon is involved in p bondingto the other carbon

p

2 sp2

sp Orbital Hybridization

2 equivalent half-filled sp hybrid orbitals plus 2 p orbitals left unhybridized

2p

2 p

2 sp

2s

sp Orbital Hybridization

2 p

1 of the 2 sp orbitalsis involved in a s bondto hydrogen; the otheris involved in a s bondto carbon

2 sp

p Bonding in Acetylene

the unhybridized p orbitals of carbon are involved in separatep bonds to the other carbon

2 p

2 sp

Three Models

Lewis

most familiar—easiest to apply

Valence-Bond (Orbital Hybridization)

provides more insight than Lewis model

ability to connect structure and reactivity to hybridization develops with practice

Molecular Orbital

potentially the most powerful method

but is the most abstract

requires the most experience to use effectively

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