Chemical bond myself

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Chemical bond

Chemical bonds

Fulfils the octet arrangement rule

covalent bondsIonic bonds

Metal ion donateselectrons Non-Metal ion acceptselectrons

Sharing of electrons

among non-metal atoms

Single bond

Cation Anion

Double bond

Triple bond

Covalent compound

Electrostatic attraction

Used as organic

solvent

Physical properties

Electricalconductivity

Melting and boilingpoint

Solubility Volatility

Ionic compound

Concept

Map



Why and how atoms combine

Lewis diagrams

� When atoms combine, only electrons in the

outer (valence) shell are involved.We canrepresent these valence electrons with Lewis

diagrams.



Drawing Lewis StructuresDrawing Lewis Structures

� Follow Step by Step Method (See Ng Web-site)

� Total all valence electrons. [Consider Charge]

� Write symbols for the atoms and guess skeleton

structure [ define a central atom ].� Place a pair of electrons in each bond.

� Complete octets of surrounding atoms. [ H = 2 only ]

� Place leftover electrons in pairs on the central atom.

� If there are not enough electrons to give the centralatom an octet, look for multiple bonds by transferringelectrons until each atom has eight electrons around it.



Chemical Bonds, LewisChemical Bonds, Lewis

Symbols, and the Octet RuleSymbols, and the Octet RuleLewis Symbols




Symbols, and the Octet RuleSymbols, and the Octet Rule� The Octet Rule

� All noble gases except He has an s2p6

configuration.� Octet rule: atoms tend to gain, lose, or

share electrons until they are surrounded

by 8 valence electrons (4 electron pairs).

� Caution: there are many exceptions to the

octet rule.



� The Octet Rule

The noble gasses do not react with other

elements. In other words, noble gasses arevery stable. Let¶s look at the electron

configuration of noble gasses (note: K is the

name given to shell 1, L to 2, etc.)

� Most Noble gasses have 8 electrons in their

outer shell. This is a stable conformatio

� When atoms form ions or combine in

compounds they obtain electron

configurations of the nearest noble gas

(usually this means that there will be 8 outer

electrons)



Element Shell

K L M N O P

� He 2 � Ne 2 8

� Ar 2 8 8

� Kr 2 8 18 8� Xe 2 8 18 18 8

� Rn 2 8 18 32 18 8




Symbols, and the Octet RuleSymbols, and the Octet Rule

� Chemical bond: attractive force holding two or more atoms together.

� Covalent bond results from sharing electronsbetween the atoms. Usually found betweennonmetals.

� Ionic bond results from the transfer of electrons

from a metal to a nonmetal.� Metallic bond: attractive force holding pure

metals together.



� Ionic bonding occurs between metals and non-

metals.

� Covalent bonding occurs between two non-

metals. (When two metals combine an alloy isformed. Alloys are unusual substances; we will

not concern ourselves with bonding in alloys)

� Na + Cl = Ionic

(metal) (non metal)

� H + O = Covalent

(non metal) (non metal)



Exercise

� Identify each compound as ionic or

covalent: MgO, CaCl2, SO2, PbCl2, CCl4,

CH4



The Formation equation of ion

Sodium atom release 1 electron form Sodium ion

Na y Na + + 1e

2.8.1 2.8 ( = Ne) chlor chlor atom receive 1 electron form chlor ion

y y y y1 -

: Cl y + e : Cl :y y y y

2.8.7 2.8.8 ( = Ne)







Forms of Chemical Bonds

� There are 2 extreme forms of connecting or

bonding atoms:

� Ionic²complete transfer of electrons from

one atom to another

� Covalent²electrons shared between

atoms

18, 20 Oct 97 Bonding and Structure 14

Most bonds are somewhere in between.



Formation Ionic bond :Na + Cl

ClNa

NaCl

[ Cl ]1±

[Na]+ [ Cl ]1±

[Na]+

+





Ionic bonding: Li + OIonic bonding: Li + O

3p+

4n02e-1e-

3p+

4n02e-1e-

1e-

1e-

6e- 2e-

8n08p+ 8e- 2e-8n08p+

3p+

4n02e-

3p+

4n02e-

OLi

Li

[ O ]2±

[Li]+

[Li]+



� 2Li+ + O-2 Li2O



Ionic bonding: Al + ClIonic bonding: Al + Cl

Al Cl

Cl

Cl

[ Cl ]±[Al]3+

[ Cl ]±

[ Cl ]±

Al3+ + 3Cl- AlCl3



Figure 8.3: Ionic BondingFigure 8.3: Ionic Bonding



Conclusions

� Ionic bonds are also known aselectrovalent bonds.

� The metal atom forms a cation by donatingits electron to the non-metal atom. Thenon-metal atom forms an anion when itreceives the electron donated by the metalatom.

� Ionic bond formed the anion (negative ion)is attracted to the cation (positive ion)



� The force of attraction between the two

charged ion is called the electrostatic

force.

� Ionic bonds are very strong due to the

electrostatic force between the ion.

� The ions in an ionic bond can be

separated by chemical reaction



Exercise

1. Predict the ionic compound formed from

reactions below!

a. 19K and 16S b. 20Ca and 8O2. The atomic number of P,Q,R and S are

,9,11,12 and 18. which pair of atoms will

form ionic bonds?

3.What are the properties of ionic

compound?



Formation of covalentbonds



Covalent Bonding

� Covalent bond is the sharing of the

VALENCE ELECTRONS of each atom in

a bond

R ecall: Electrons are divided between coreand valence electrons.

ATOM core valence

Na 1s2 2s2 2p6 3s1 [Ne] 3s1

Br [Ar] 3d10 4s2 4p5 [Ar] 3d10 4s2 4p5

Br Br



Valence Electrons1A1A

3A3A2A2A 4A4A 6A6A 7A7A

8A8A

5A5A

Number of valence electrons isequal to the Group number .



ElectronElectron

Distribution inDistribution in

MoleculesMolecules

� Electron

distribution isdepicted with

Lewis electron

dot structures

� Electrons are

distributed as:

� shared or BOND

PAIRS and

� unshared or LONE

PAIRS.G. N. Lewis

1875 - 1946



Bond and Lone Pairs

� Electrons are distributed as shared or BOND

PAIRS and unshared or LONE PAIRS.

��

H Cl��

�Unshared or

lone pair (LP)

shared or bond pair

This is a LEWIS ELECTRON DOT structure.



Covalent Bonds

� One or more pairs of

electrons are shared

by two atoms



Formation covalent bond

�HCl - Single Covalent� O2 ± Double Covalent

Cl HH

Cl

H Cl

or with lines representing bonds

OO

OO

OO

or with lines representing bonds



Exercise� Draw Lewis dot diagrams to represent the

following compounds (think about whether

they are ionic or covalent): CCl4, , MgF2,

H2O, NH3, NaCl, N2, H2





Covalent bondingCovalent bondingQ7

CCl4 - Covalent

C

Cl

ClCl

Cl

HCl - Covalent

H Cl

MgF2 - Ionic

[ F ]2±[Mg]2+

H2O - Covalent

H O H

NH3 - Covalent

H N H

H

NaCl - Ionic

[ Cl ]±[Na] +

OH± - Covalent

O H

H2 - Covalent

H H

For more lessons, visitwww.chalkbored.com



MultipleMultiplebondsbonds

Do Q. 8. Build models of molecules,O3 as challenge (can¶t build it or ionic)

HCl - Covalent

H Cl H Cl

CO2 - Covalent

C OO

Na2O - Ionic

[ O ]2±[Na]2+

H N H

H

H N H

H

OO

OO

O2 - Covalent

OO C

II

II

I2 - Covalent

[ O ]32±[Al]2

3+

Al2O3 - Ionic

NH3 - Covalent

OO O

O OO

O3 - Covalent

H C H

H

H

H C H

H

H

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Chemical bond myself

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