CH203 Lecture 2September 8, 2009

John. A. Porco, Jr.

Department of Chemistryporco@bu.edu

This is incorrect (Figure 1.4 in text)

Review of Lecture 1: Atomic Structure: Electron Configurations

• Ground-state electron configuration of an atom lists orbitals occupied by its electrons. Rules:

• 1. Lowest-energy orbitals fill first: 1s → 2s → 2p →3s → 3p → 4s → 3d (Aufbau (“build-up”) principle)

• 2. Electron spin can have only two orientations, up ↑and down ↓. Only two electrons can occupy an orbital, and they must be of opposite spin (Pauli exclusion principle)

• 3. If two or more empty orbitals of equal energy are available, electrons occupy each with spins parallel until all orbitals have one electron (Hund's rule).

What do ``shared'' electrons actually look like?

1) 2)

The sequence shows how electron density changes as two H atoms are brought closer together until they reach their true bond length

3)

Hybridization: sp3 Orbitals and the Structure of Methane

• Carbon has 4 valence electrons (2s2 2p2) • In CH4, all C–H bonds are identical (tetrahedral) • sp3 hybrid orbitals: s orbital and three p orbitals

combine to form four equivalent, unsymmetrical, tetrahedral orbitals (sppp = sp3), Pauling (1931)

Hybridization: sp2 Orbitals and the Structure of Ethylene

• sp2 hybrid orbitals: 2s orbital combines with two2p orbitals, giving 3 orbitals (spp = sp2)

• sp2 orbitals are in a plane with 120° angles • Remaining p orbital is perpendicular to the plane

90° 120°

Hybridization: sp Orbitals and the Structure of Acetylene

• C-C a triple bond sharing six electrons• Carbon 2s orbital hybridizes with a single p orbital

giving two sp hybrids– two p orbitals remain unchanged

• sp orbitals are linear, 180° apart on x-axis• Two p orbitals are perpendicular on the y-axis and

the z-axis

Orbitals of Acetylene• Two sp hybrid orbitals from each C form sp–sp σ

bond• pz orbitals from each C form a pz–pz π bond by

sideways overlap and py orbitals overlap similarly

The Periodic Table and Electronegativity

Bond PolaritiesBond Diff in EN Negative atom Type of Bond

H - H 0.0 N/A pure covalent

C - H 0.4 C (weakly) polar covalent

O - H 1.4 O polar covalent

H - F 1.9 F polar covalent

S - O 1.0 O polar covalent

C - O 1.0 O polar covalent

Al - C 1.0 C polar covalent

Na - Cl 2.1 Cl ionic

Li - F 3.0 F ionic

Mg - O 2.3 O ionic

Mg - C 1.3 C polar covalent

Less than 0.5 difference in EN : Nonpolar covalent0.5 to 2 EN units – Polar covalentGreater than 2 EN units - Ionic

ct{ 2-03

C b . , h c a h o n /

lzcLure

ttt i

3 A

4 E

7 y

7 s

Lck& # Z

ql;/ oJ?o8

Corf'ahon fv- v^ lo s L

C4wvnrical $oJ s

Sl"e,tl tt'*f'rl s

a- An e- o c l^e'+, T ' t n

EP"ct ^f

n fh.. or krwosL

shb , l , )

lncofrcct-)

T. I

. o , l s ' ? s z z p ( .

3sz 3 f t

Y s " 3 d I

f i o ( ie Io

l r o - f g A t s 2 - Z s z Z f I

ohwi c # U

tt t.t TJ fl+ l - ' - G r, r v

J! .-!l 1$J-L

-g- .1 ' N€o n

Abw,s C lo S< . r b h i l lQ - o f

f nDd t c khk - ^ ch ru i< { " z . i , by

Jt"^ fln1 e- S '

? sl^ate-ol e- bo^J

Cov a l .n L h ' , . J -S ( n vo( ve s l , -o ' rcm/

o f e - t l * l ^ ^ ' < ' 1 ^ , ' h > w t f l ' " ' f u f u t t

t ( I t . . , - {l ruo(z-c. l tas

t ) col laehon uf ofuL'^ ' r

hp(d, h3illa*r \ covatk '^-F b"--d 1. '

Lf P +- | Ht ttLo(zc uQ. )

Hz fuol-cu le

H . + - H - -.>

Skovt f €^5 oF VaQ a"cz. Sl4ll

CH rt btr,ok-cu (C-

H: t ltu-1^--

le.uisoLo f-

Sfwcfurz?+

o- ll ̂ H

L(ekvQ

Sln c.lu.e-

CIr's b"+Jybuelo*)

L

H iH -C-Ff

a r l

H

,' ? ' t t H ,

Ho a

- ) [ t ; C ' .e 3

hc, . svr voUecL e-s

-* tP'

= VpA",o frtA

Ll LaoJ s

7e,- C clta-a4

h"4 =

Irrv-NohU b^ t

" c^f ixK r s o r

ockL .rh ,.*l

Vakncs. I "f o

r - O

q Jh o s

6r*s

S r x

lr'o

Va-Qa-<

bo^J s

vwoz- aT)

zsz Lp V

H-- g-.. H( ne.ds z

2 H

+-

a a

, 1 . A 'a a t Dr L . V .

Ha .

;? '

VaQ.ac ts " fIV

7

,F l\)

"vt

h,-S

firv*. t

fit''e-Ioo^J (.

t / . r \

vae ra.-ca e-f \Zs L Zpt )

e , g H 3

] - - H : N : Ha a

A,&nh^ ,on (<

n Ol\- l'2 p4tr ^ ? o f

(st"e,- pair €-- 5

ntr{-- U SoA (.r, bo4;^3

j H .

HybnJ ( i - - ' ho n oF ohwi c ohJ* l s

d , f f . Qt*c.a-( Q u-l f

cl n

srh tL(

t'rJ!_1v

rA\ (-{ o v*ettlf

Ayv tvc&z . l '

--* s fbt h^t f

- r . orbrb l

o rhrL^'l f

r arz

t{fhr r-.rr-

\ e

?-g

l S

n-p

f,ir CH rl

Cl , r L (

k" obl"h ^

t s

h r Y , t t 6 ' ^It lr

h '1hn&t %, 'A on

1 ^ l (

r t o ) .

h lbnJ

C-F{ ho4 r qC-

Ho u, i I flt-* 7

t*. L4,r or{t t k( r

Cot*-hrrx- f i p

4kraai c o4rt^/7

t

l s - t

'"( I* IFL+A, I, 'e

/ L{-" k'c\h/ ( / o( sf 3 o'bb't r

tIn*.a,-l9f7 hvb nlJ

5f1 v.Vt, o/r C

gnA-/' tna w'lL*( ; o t u r L l t

an-! L q

td<-..lvc^ | c Ft bo-l t

{

sflu"Hor'. l{

S f 3 o r b r u r - l s oArH L o . * !

q d r y U o F ̂

( n d"-.cL +{^e

{*he* +t

l o n 4 . C f , 5 r " . c ) ) h r^J

At rccL t ,l r c rOvt 4- f fkXr o f ,

nt rOb i

s p 2' h.rbn4 saarhon

Yh.A^\'1 tvn orln ̂ L

LJ,\r,oh C ahrn^ f

vah' - q^ "$1'g2

l.t' L =c/Fi

hto(e er* S e>( | SL | ,r

,^o'q-. FA.^* LZ-S

Oaaa sq

IL*tr<.

a,lo rn"

.(Llh"e/ \| ' u

h r -

.

t t ,

c : : ct

. l

3rn *{.tt S Cot t<-

Lav-lat.^"J lA'/. I't-

' t -p Drhrl- ' ; l 5h 1 h n J f + o n . .

1r"

.S o'.h a l-'l

\o ? t = c a/

- \

h\ -,1=:1 )rts'c

H \-'l L t ' c

L

7

- , ) sp- vrtd^q^y, P

, f t ,A - )

h c b " 4 f n r t ^ Jb 1 , f t - s F z

- . , \ ) r , t ^ " 1 k n J ' 1 e J

y t r ( f f ) bu^J

o rh ,kJr

z ?

6 t-c r(* p

@frr h^

j f b o ^ d J h " t € { L l e - J

^ n c !

f r^s c - c d o - b Q b o , ^ . r !

ISf hrbr td r t '<h on

\ ' n o /Vr t .^ t\ ^ y \ n n d

H ' , C : : : c ; H

h - ' a l C - HS--)l S o o

3..1 Ut, ̂ , J d A

Ca,r bon u''-- o'f f o

{or'^ 'r. h fr| ,* *il

bv sL*^n'.3 0 [ g-,

( , *.., {-

o Sf - l^-th rt) ' r*' A

jo , *z- l I 'Y rP-sP

a^-\ Z'fl- load S

c^

ff

tuI ,n- . . -oQ.c-Qa- ec(u,J

f1rI^/ 'Q hoJ

,ruA

q l^ \.^- J Trlh,rJL

bo,- ,J o 'h"$n I

orb' hl

S ph1b4 JSu tn

bo,*d UyA C ft")

l z o

r33

tE+

l o ' t u ,

C = L

C = C

C * C

o'b, l^l-r

fto*l,J + e-

Sechon I , l l

**drerr

t^,e- r,'t ll fr Lv S sr

voUn Lt bu*d

( h1b . , d o ,h rz , i c

Accour, (_ ft n

Pw\ =

/^ O 1-r* e *) ) q lt . otp p.o^ "t,

I a v,E(.rt ,. 3 t4^a,l* a orh, ̂ |

(e v*la t .., -.h a- oF

*J* t tc oLtL. \ - i

ho {o, o^ ltn o bc tLq.r o-btl='/r

ofProactus oh

&ua

Sl*re

CI^ 'F i . . - r L ' , f o (a r C tu+Qa l

Bo^ls -b f tc iJs E ' 6q1.cS

S k , p s c c h o n s L , Z r Z , l 3

9.obb,^ t t-l.,

8 , q t ( o l l 5 ) 2 5 , 3 a t 3 3 1 3 1 ,

3t , 3$ t71 , 4D 1L{ ( rq?) tV , €s , r ( ,Ic 5 gI

Cl^op h,r

k i J s

L .I

tI

/e e {ar

$ " P s

( o u o Q n l * $ o , ^ J s -

t+X

Lt

l s z Zs

Ftsz 7r' zf '

P ote.^( o d a b * l '

bo^ l#

l D ^ i C

Ct -rt ck ri o^ ,c b o^ l i

t vJ

l C i \ ( C -

b o ̂ /

9 . o

F

el*lrlrrcJah*"b

[ ^

v X

/; r@

\y

..-tn * h' ul4t* cl e- t

t ^ { . * S , t * S * b ' t ' \ o F ' ' ^

( arb,ho^l Sc*t+\

, t i k - J o * C f r S t A '

h)* Fn,- l&l

h o r . ( o . . ) u F W

l . o

Li fJe. c l') 0

wr hc^ I

F ?r (t )

t q e r t * V 5

F 4 \cr I6 r l

L {

l,^ 1,fctw A7 EN I( ^ v * h , o C c * f t

Co (,rr-rr ( lnh^) oa hr*v6,tf ui la( ial t t

Cn d4Lf , l'gf,oul- -

lm+r1 f*r. uf e's t $ l4cf '

Et.lh*l' f, ' '- 1[*6. oF (+' r.uclr vt

X O XS y,'n* ,

co v* le aL

b o ^ )

L , 3 .

h H

a b.a,^7 c S

St'qrrl e 6v^ll1

b1 t6vt..) Ca l o * l

El r . {T " t jLwl

f ^( (e^Y t

Y L n o d ' c

a"A t o r ^ t u f A