上海交通大学：《大学化学》教学资源_加州理工课件学习_Series10HybridizationPart1

Hybridization Reading:Gray:(4-1),(4-2),and (4-4) 0GC:(6.2.6),(6.4)and(6.5) X-1

Hybridization Part 1 Reading: Gray: (4-1), (4-2), and (4-4) OGC: (6.2.6), (6.4) and (6.5) X-1

The story so far: MO-LCAO works great for diatomic molecules! But... What about other numbers of atoms? Will MO-LCAO work for polyatomic molecules? X-2

MO-LCAO works great for diatomic molecules! But... What about other numbers of atoms? The story so far: Will MO-LCAO work for polyatomic molecules? X-2

Let's try BeH2 We know: BeH,is a linear molecule,by VSEPR. H Be H Bond angle:180° The electron configuration of BeH,is Be:1s2 2s2 H:1s1 1s- 1s X-3

Letʼs try BeH2 We know: • BeH2 is a linear molecule, by VSEPR. • The electron configuration of BeH2 is H Be H Be: 1s2 2s2 H: 1s1 1s 2s 2p 1s Bond angle: 180° X-3

Make MO's: First bond H and Be Next bond H and BeH to form BeH to form BeH2 O* O* n 2p 1s 1s 2s H+BeH←一 Be BeH→BeH2—H The MO's for BeH,are complicated and hard to work with. X-4

H BeH Be 2s 1s 2p σ* πn σb σb BeH 1s σ* σb σb πn σ* πn σ* σb BeH2 H Make MOʼs: First bond H and Be to form BeH Next bond H and BeH to form BeH2 The MOʼs for BeH2 are complicated and hard to work with. X-4

Attempt to make a graphical model of BeH2: Be:1s2 2s2 H:1s1 H:1s1 1s 1s 2s 1s H H Be 1s H)is H Be 2s H+Be 1s 1s 2s 1s 2pz 2pz Are any of these models reasonable? X-5

Attempt to make a graphical model of BeH2: Are any of these models reasonable? ? 2s 1s H Be H 1s + Be: 1s2 2s2 2s 2pz + + 2s 2pz H Be H 1s 1s + + H: 1s1 1s + H: 1s1 1s + 2pz H + Be H 1s 1s X-5

Attempt to make a graphical model of BeH2: Be:1s2 2s2 H:1s1 H:1s1 1s 1s 2s 1s H Be 1s 1s H+ Be 2s H+Be 1s 1s 2s 1s 2pz 2pz These two are no good: One orbital can't hold four electrons X-6

These two are no good: One orbital canʼt hold four electrons ? 2s 1s H Be H 1s + Be: 1s2 2s2 2s 2pz + + 2s 2pz H Be H 1s 1s + + H: 1s1 1s + H: 1s1 1s + 2pz H + Be H 1s 1s Attempt to make a graphical model of BeH2: X-6

Attempt to make a graphical model of BeH2: Be:1s2 2s2 H:1s1 H:1s1 1s 1s 2s 90° 1s H H Be 1s 2s 2pz 2pz This one is no good: According to VSEPR,the bond angle should be 180

90° This one is no good: According to VSEPR, the bond angle should be 180°. ? 2s 1s H Be H 1s + Be: 1s2 2s2 2s 2pz + + 2s 2pz H Be H 1s 1s + + H: 1s1 1s + H: 1s1 1s + 2pz H + Be H 1s 1s Attempt to make a graphical model of BeH2: X-7

Attempt to make a graphical model of BeH2: Be:1s2 2s2 H:1s1 H:1s1 + 1s 1s 2s 1s 1s 2s 2pz 2pz Unfortunately,none of these models make sense. X-8

Unfortunately, none of these models make sense. ? 2s 1s H Be H 1s + Be: 1s2 2s2 2s 2pz + + 2s 2pz H Be H 1s 1s + + H: 1s1 1s + H: 1s1 1s + 2pz H + Be H 1s 1s Attempt to make a graphical model of BeH2: X-8

hybridized the orbitals... Maybe if we blended the orbitals together... Be 2s 2pz 2s 2pz 2 sp hybrids □ X-9

Maybe if we blended the orbitals together... hybridized the orbitals... 2 sp hybrids + 2s 2pz + 2pz + + 2s Be X-9

Hybridization in terms of electron configuration: Unhybridized Be 2p 2P2 2px 2s Decouple 2s 1s 计 electron pair ○1s X-10

Hybridization in terms of electron configuration: 2pz 2s 1s 2s 2p 2py 2px 1s Decouple electron pair Be Unhybridized X-10