c002 b -Bonding Lecture1

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Ikatan, & Struktur



Simbol Lewis

Mewakili bilangan elektron valensi sebagai titik.

Nombor valensi sama dengan nombor kumpulan

dalam Jadual perkalaan Unsur

H

Li Be B C N O F Ne

He

Na; Is2, 2s2, 2p6, 3s1 = [Ne] 3s1

Lewis Structure = Na

Sebagai contoh ,

Kumpulan 1 2 3 4 5 6 7 8





Gas Lengai (Adi) mempunyai konfigurasi elektron stabil

Ar

e; s , s , pAr; [ e] s , p

a + a+

+ [ ]

_

Konfigurasi elektron bagi eon dicapai untuk kedua unsur

Contoh ikatan ionik

09



Tulis keadan aras konfigurasi elektron bagi unsur-unsur berikut:

1) Neon (10) 1s2 2s2 2px2 2py

22pz2

2) Argon (18) 1s2 2s2 2px2 2py

22pz2 3s2 3px

2 3py23pz

2

3) Nitrogen (7) 1s2 2s2 2px1 2py

12pz1

4) Oxygen (8) 1s2 2s2 2px2 2py

12pz1

5) Chlorine (17) 1s2 2s2 2px2 2py

22pz2 3s2 3px

2 3py23pz

1

6) Sodium (11) 1s2 2s2 2px2 2py

22pz2 3s1



Ikatan Ionik dikaitkan dengan daya elektrostatik antara ion-ion,

biasanya satu kation logam dan satun anion bukan-logam

iIkatan Kovalen terhasil daripada perkongsian dari 2 elektron antara

dua atom dalam molekul, biasanya atom bukan-logam.

There are two types of bonding;

M enggunakan hukum Oktet

l l ll

+

number f electr ns r und each at m e

+

number f electr ns ar und each at m r

+

number f electr ns ar und each at m e

Ti ap i katan kovalen mempunyai 2 elektron

Ikatan T r i pel



H

CH H

H

methane

Car bon has alence electr ons

C

H

H

H

H

H C

Ne

Neon

Stable ctet r equir ed

Ikatan Kovalen ² Atom-atom berkongsi elektron



Molekul Hidrogen, H2

K epekatan cas negat if antara dua

nukleus terjad i d i dalan i katan kovalen



Carbon dioxide, CO2

Double bonds

O O C OC O C OO+ + =



E lectronegat i v i ty is defined as the ability of an atom

in a molecule to attract electrons to itself

Prof. Linus PaulingNobel Prize for Chemistry 1954

Nobel Prize for Peace 1962

E lectronegat i v i ty is a function of two properties of

isolated atoms;

The atom¶s ionization energy (how strongly an atom

holds onto its own electrons)

The atom¶s electron affinity (how strongly the atom

attracts other electrons)

For example, an element which has:

A large (negative) electron affinity

A high ionization (always endothermic, or

positive for neutral atoms)

Will: Attract electrons from other atoms and Resist having electrons attracted

away

Such atoms w i ll be hi ghly electronegat i ve



P aul i ng scale of electronegat i v i ty;

Fluorine is the most electronegative element followed by O and N, Cl are

equal third. Cs is least.

Electronegativity i ncreases f rom lef t to r i ght along the Periodic Table.

For the representative elements (s & p block), the electronegat i v i ty

decreases as you go down a group.

No trend in the transition metals.



+

3 sp3 orbital kacukan

Orientasi tetrahedron

Sudut ikatan = 109.5S

H

HH

H

109.5

W

WWW

2s2

2px1

2py1

2s1 2px

12py

12pz

12pz

0

K acukan - campuran orbital s and p

eg. Metana CH4

Campuran orbital: 1 s and 3 p



Struktur & Ikatan

Apa jenis Orbital?:

CH3CH2CH3

sp3 sp

3sp3

sp

C

H

C

sp2 sp2

H2C CH

sp

C

H3C

sp3

sp2

sp2

sp3

H

sp3

sp2

C CH2

H3C

H3C

sp3

sp2

C

C

C

C

C

C

O

H

O

O

C

O C

H

H

H

sp2

sp2

sp2

sp2

sp2

sp2

sp2

sp2

sp2

sp3

sp3

sp3



Gambaran struktur & ikatan



Struktur & ikatan

Formula Kimia: C6 1 formula molekul

C

C C CCC

Line-Bond or Kekule

H3C C

H2

C

H

CH3

C

HC

H2

Condensed formulas

H3C CH2

H

CH3

line or structural formulas

H

H



Berapa banyak ikatan?

H F Cl Br O

N B C



Ubah formula berikut kepada struktur-garis:

C3H8

C2H6O

H C

H

H

C

H

H

C

H

H

H H3C CH3

H C

H

H

C

H

H

O H H C

H

H

O C H

H

H

OH

O



C2H4O

C3H9N

H C

H

H

C C C

H

H

CO

O

H

O H

H

H

H

OH

OH

H

H

H

O

H C

H

H

C

H

H

C

H

N

H

H H

H C

H

H

N C

H

H H C

H

H

C

H

H

N

H

C

CH

H

H

H

H

H

H

NH2 NN

H







21

Acids and Bases

---an introduction to organic reactions

CH3 CH3

H O2

HO Cl-

Na OH Cl-

Na

Substitution

s

Additions

CH3CH=CH2 +HBr CH3CHBr CH2H

Elimination

s2 5

C H ONa

2 5C H OH

55o C

2 5C H OHBr NaCHCHCHCHCHCH 3

Br 2

3 + +2

H



22

Brønsted-Lowry¶s defination:

An acid---a proton donor; a base---a proton

acceptor

Acid-Base Reaction

OH

H

+ H Cl H O

H

H+

+ Cl-

AcidBase Conjugate acidConjugate base

hydroniu

m

HA + H2O H

3O+ + A-K ? A? A

? A? AOH HA

AOH K

2

3

�!

? A ? A? A? AHA

AOH OH K K

a

�3

2? A ? A

? A

�

A

HAK OH

a

3



23

? A ? A

? A? A? A ? A

? A ? A? A? A

? A¹¹

º

¸©©

ª

¨!

!

!

!!

1log

log

log

logloglog

0

0

0

3

HA

HApK

HAHAHApK

HAHA

HApK

A

HAK OH pH

a

a

a

a

pKa < 1 a stong acid, pKa > 4 a weak

acid



2

4

The Lewis Defintion of Acid and Base---an

extension

Acids: electron-pair acceptors

Bases: electron-pair donors

B

Cl

Cl

Cl

B

H

H

H+

H HC

H

H

+ AlX3( )

M X2

M X2

M X2

AlX3( )

AlX3( )

C+Al

Cl

Cl

Cl

Lewis Acids

compared with Brønsted Acids: without donating protons



25

Lewis Bases

OH(R)-

H O H N H

H

H

Lewis acid-base reactions:

l

Cl

Cl

Cl + N

CH3 HC

HC 3

HC 3

Al

Cl

Cl

Cl N- +

CH3

CH3

general organic reaction

Lewis acid Lewis base

nucleophiles



26

H A-

H A-

++

From left to right: dissociation of a Brønsted Acid

From right to left : combination of a Lewis Acid and

Base

electrophiles

nucleophiles



27

Exercise:

32,33,35,37,40,41,50,52,53,54,55,56

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c002 b -Bonding Lecture1