10.covalent bonding and octet rule

8/8/2019 10.Covalent Bonding and Octet Rule

http://slidepdf.com/reader/full/10covalent-bonding-and-octet-rule 1/44

Now .let us seeNow .let us see

the Covalentthe CovalentBonding.Bonding.



COVALENTCOVALENTBONDINGBONDING



Most substances thatMost substances thatwe see are not ionicwe see are not ionic



They are notThey are notcollections of collections of electrically chargedelectrically chargedparticles (ions), butparticles (ions), but

are electricallyare electrically

neutral combinationsneutral combinationscalledcalled moleculesmolecules ..



FOR EXAMPLES:FOR EXAMPLES:HH22O ,O ,

CC1212 HH2222 OO 1111

CC66HH

1212OO

66



Lewis SymbolLewis SymbolTo keep track of valenceTo keep track of valence

electrons, a system of symbols,electrons, a system of symbols,calledcalled Lewis symbolsLewis symbols waswas

designeddesigned



Lewis SymbolLewis SymbolThe lewis symbols for all eightThe lewis symbols for all eight

AA--group elements of period 2 are:group elements of period 2 are:



Lewis SymbolLewis SymbolTwo electrons shared between twoTwo electrons shared between twoatoms are shown as a pair of dots ( atoms are shown as a pair of dots (:) :)

or dashes ( or dashes ( ) placed between the ) placed between thesymbols of the two bonded atomsymbols of the two bonded atom

H:HH:HHH--HH



Lewis SymbolLewis Symbol

S ince electrons areS ince electrons are

shared in the Hshared in the H 22molecule, each atom Hmolecule, each atom Hconsidered to have twoconsidered to have twoelectrons.electrons.



Lewis Sy mbol ofLewis Sy mbol ofHidrogen MoleculeHidrogen Molecule

H H

Shared electron pair

Circle indicates that there are two electronsin the valence shell of each hydrogen atom



11

Covalent BondCovalent BondandandThe Octet RuleThe Octet Rule



Atoms wich are Atoms wich are

unstable, wantunstable, wantto be stableto be stable



U suall yU suall y , stable, stableatoms haveatoms havenoble gasnoble gas

configurationconfiguration



Questions

QuestionsW hat is a covalentW hat is a covalent

bonding?bonding?How does it occur?How does it occur?

W h y does atom makeW h y does atom makecovalent bonding?covalent bonding?



a.a.The F ormation of The F ormation of

ClCl 22



Atom Cl Atom Cl

C l

1s2 2s 2 2 6 3s2 3 5

K L M

Paire electro

U aire electro



Chlorin AtomChlorin AtomConfiguration?Configuration?Group of Atom?Group of Atom?

Valence Electrons? Valence Electrons?

Octet?Octet?Stable?Stable?



Chlorin AtomChlorin Atom Atom chlor tends to obey Atom chlor tends to obeythe octet rule by sharing of the octet rule by sharing of electrons with other atomelectrons with other atom

to form covalent bondto form covalent bond



Covalent Bond andCovalent Bond and

The O ctet R uleThe O ctet R uleWhen atoms form covalent bonds,When atoms form covalent bonds,

they tend to share sufficientthey tend to share sufficientelectrons so as to achieve an outer electrons so as to achieve an outer shell having eight electronsshell having eight electrons

(except for hydrogen and helium,(except for hydrogen and helium,which have a stable outer shell of 2which have a stable outer shell of 2electrons).electrons).



TheF

ormation of ClTheF

ormation of Cl 22B efore they join, the thirdB efore they join, the thirdshell M (which contain ofshell M (which contain of3s and 3p orbitals ) of3s and 3p orbitals ) ofeach Cl atom is only 7 each Cl atom is only 7

electronelectron- -filled.filled.SeeSee periodic tableperiodic table



The Formation of ClThe Formation of Cl 22W hen each chlorine atomW hen each chlorine atom shares shares

its unpaired electron, both atomsits unpaired electron, both atomshave a full valence of eighthave a full valence of eightelectrons (OCTET).electrons (OCTET).



The Formation of ClThe Formation of Cl 22Once the bond is formed,Once the bond is formed,

energ y is released, and theenerg y is released, and thenew chlorine moleculenew chlorine molecule(Cl(Cl 22 ) behaves as a single ) behaves as a single

particleparticle



This energ y is calledThis energ y is called

thethe bondbond energ y .energ y .



b.b.

The F ormation of The F ormation of HH22



Hidrogen AtomHidrogen Atom

H



Hidrogen AtomHidrogen AtomConfiguration?Configuration?Group of Atom?Group of Atom?

Valence Electrons? Valence Electrons?

Octet?Octet?Stable?Stable?



Before they join, the 1sBefore they join, the 1sorbitals of each H atom isorbitals of each H atom is

only half only half- -filled.filled.

HK

+ HK



When they join, they share each other'sWhen they join, they share each other'selectrons, filling each other's 1s orbitalelectrons, filling each other's 1s orbital

pair.pair.



c.c.

The Formation ofThe Formation ofHClHCl



1 . Atom Hidrogen1 . Atom Hidrogen

How the y joint toHow the y joint toshare electrons?share electrons?

H K

2. Atom Chlor2. Atom Chlor

Cl K



The Formation of HClThe Formation of HCl

C l K L MH K +

C l K L MHK



The Formation of HClThe Formation of HCl

b y Lewis S tructureb y Lewis S tructure



Some atoms (nonSome atoms (nonHidrogen) such asHidrogen) such as

Carbon, Nitrogen andCarbon, Nitrogen andOx ygen can form moreOx ygen can form more

than one covalent bond.than one covalent bond.



For example, carbon can formFor example, carbon can form4 bonds (4 valence electrons),4 bonds (4 valence electrons),nitrogen can form 3 (5 valencenitrogen can form 3 (5 valence

electrons), and ox ygen canelectrons), and ox ygen canfrom 2 (6 valence electrons)from 2 (6 valence electrons)



The covalent bond can alsoThe covalent bond can alsoformed between atoms informed between atoms inpol yatomic ions such as:pol yatomic ions such as:

Hidronium ion,HHidronium ion,H 3 3 OO++

Ammonium ion, NH Ammonium ion, NH 44++ ,,

Hydroxide ion, OHHydroxide ion, OH --



Hidronium ion, HHidronium ion, H 3 3 OO++

H O H

H

+

OR

H O H +

H



Ammonium ion, NH Ammonium ion, NH44

++ ,,

H N H

H

+H

H H

+

H

H



Hydroxide ion, OHHydroxide ion, OH--

OR O H-

O H-



Two Kinds of Pair of ElectronsTwo Kinds of Pair of Electrons

H OH

L one air Electron

Bon in air Electron



ConclusionConclusionA Chemical Bonding thatA Chemical Bonding that

result when atoms shareresult when atoms shareelectrons is calledelectrons is called ::

Covalent BondingCovalent Bonding



ConclusionConclusionCovalent Bonding occursCovalent Bonding occurs

when an atom tends to obe y when an atom tends to obe y the octet rule or noble gasthe octet rule or noble gasconfiguration b y sharing ofconfiguration b y sharing ofelectrons with other atomelectrons with other atom



ExercisesExercises

Please Discuss, the formationPlease Discuss, the formation

of molecules below.of molecules below.

PHPH 44+, H+, H 22S , PHS , PH 33 , CH, CH 44 ,,HF, NHF, N 22 , ClBr, Br, ClBr, Br 22

10.covalent bonding and octet rule

Documents