Download Chemical Bonding

CHAPTER 2
Chemical Bonding
SYLLABUS
-
sCOPE OF SYLLABUS -
in and after MARCH 2023- CHEMICAL BONDIG-
ELECTROVALENT, cOVALENT & CO-ORDINATE BONDING,
STRUCTURES OF VARIOUS cOMPOUNDS, ELECTRON DOT STRUCTURE.
al Electrovalent bonding:
- Electron dot structure
of Electrovalent compounds - NaCI, MgClz, CaO
- Characteristicproperties ofelectrovalentcompounds-stateofexistence,melting &boilingpotnts,
conductiuity [heat & electricity), dissociation in solution &in molten state to be linked with electrolysis.
b
Covalent Bonding:
Electron dot structure-ofcovalent molecules on the basis of duplet &octet ofelectrons
lexample: hydrogen, chlorine, nitrogen, ammonia, carbon tetrachloride, methane).
- Polar Covalent compounds - based on difference in electronegativity:
Examples HCI & H,0 including structures.
-
Characteristie properties of Covalentcompounds
stateofexistence melting& boiling points, conductivity Iheat & electricity), ionisation in solution.
Comparison of Electrovalent & Covalent compounds.
Ic] Coordinate Bonding:
- Deflnition
-
The lone pair effect of the oxygen atom of the water molecule & the nitrogen atom of
-
the ammonia molecule to explain the formation of H,0* & OH ions in water & NH4 ion.
- The meaning of lone pair the formation of hydronium ion &
ammoniumion must be explained with help of electron dot diagrams.
A. INTRODUCTION
Chemical bord is the force which holds two
1.
or more
atoms together in a stable molecule.
AN ATOM
atom is the smallest unit of matter taking part in a chemical reaction.
An
It is built up of sub-atomic particles -protons, neutrons and electrons
Two or more atoms [metallic or non-metallic) combine to form a molecule.
The force which holds the atoms together as a stable molecule is the chemical bond.
Sub-atomic particle Charge
Electron
(6p
6n
.
-Proton
Neutron
-Orbit[shell]
AN ATOM
PROTON
NEUTRON
ELECTRON e
Mass [C-12 standard]
+1
1 a.m.u.
0
1 a.m.u.
-1
negligible
Elementsare pure substances madeup or one Kind oratoms - having the same atomic number.
2 TYPES OF ELEMENTS - involved in chemical combination.
Metallic elements - have 1, 2 or 3 electrons in valence [outer] shell.
They lose 1,2 or 3 electrons and become p0sitively charged ions [cations].
Non-metallic elements -
have 4, 5, 6
or 7 electrons in valence [outer| shell.
Theygain (4),3, 2, or 1 electrons and become negatively charged ions [anions.
COMBINATION- Atoms combine to formamolecule by two means3. CHEMICAL
T r a n s f e r o f valence electrons f r o m - a metallic atom to a non-metallic atom.
Sharingof valeceelectroisbettoeen-two atoms lgenerally both non-metallic].
21
B. CHEMICAL BONDING
CHEMICAL BOND &TYPES OF BONDING Electrovalent &Covalen
CHEMICAL BONDING
Chemical bond -The linkage or force which acts between two or
more atoms
hold them together as a stable molecule. The concept
chemical bonain
NOBLE GAS
SYMBOL AT. NO.
ELECTRONIC CONFIGURATION
O
N
M
K L
He
| HELIUM1
NEON
Ne
10
2
ARGON
Ar
2
8
KRYPTON
Kr
18
36
2
18
XENON
Xe
54
RADON
Rn
86
2
2
8
8
3
18
18
32
18
18
NOBLE GASES
Have stable electronic configuration. i.e. their outermost [valence] shell is complete.
electrons in outermost shell.
They have 2 electrons in outermost shell [He] or 8 inert or unreactive.
and are
They do not lose, gain or share electrons
-
GASES
ATOMS OF ELEMENTS OTHER THAN NOBLE
i.e their outermost
Have unstable electronic configuration.
electrons and are chemically
lose,
can
They
shellis incomplete
reactive.
gain or share
-
MOLECULE
BETWEEN ATOMS TO FORM A
each atomto combine is related tothe tendency of
-
REASONS FOR CHEMICAL BONDING
T h e driving force for atoms
to attain stable electronic configuration
of the nearest noble gas.
electronic configuration it must haveFor an atom to achieve stable
shell [nearest noble gas -He]-Duplet rule
Two electrons in outermost
other than He] Octet rule
outermost shell [all noble gases
i
n
electrons
Eight
-
-
-
CHEMICAL BONDINNG
FOR ACHIEVING
in two combining
A stable electronic configuration
between them is achieved
chemical bonding
in
anotherresulting
electrons from one
valence
transfer
Electron
electrovalent or ionic com1pound.
& tormation of an
electrovalent bonding
to
atomsleading
of electrons between two reacting
of
pairs
Electron sharing
covalent compound.
and formation
to covalent bonding
METHODS
atoms
by:
atom to
of
-
of a
leading
BOND FORMATION
CHEMICAL
AFFECT
PROPERTIES WHICH
PERIODIC
1ONICCOMPOUND I.P. ofa metallic atom.
FORMATION OF
FOR
the valueofofformation of the -cation.
-|Lower
pötential
ease
Lonisation
-
-
reater the
Electronaffinity
of E.A. of a non-metallic atom.
Higher-the value
of the anion.
greater the ease orermation
between combining atoms,
the electronegativity eliference
-
-
takes
electron transfer
Electronegativity-Lar
place easily.
COVALENT COMPOUND
both atoms orelements.
electronegativity -High- between
atoms.
&c
potential,electronafifinity
between the two combining
Lonisation
negligible
be
Shoula
Electronegativity difference-
FOR
FORMATIONOF-
-
23
C. ELECTROVALENT BONDING- Electrovalent compounds
FORMATION OF-Electrovalentcompounds
involves transferof valence electro
Formation of electrovalent compounds
to another atom generally non-metalli
-
from
one
atom
-
-
generally metallic
Metallic atom
-
loses electrons
to attain stable electronic configuration
Metallic atom X[elec. config. 2,8,1]
Non-metallic atom
X - le
gains electrons
-
and becomes
X1+
and
to attain stable electronic configuration
+ le
[elec. config. 287 Y
cation
Cation [positive ion 28]
becomes an
Y-
Non-metallic atom Y
Ions cations and anions
a
-
anion
Anion .negativeion 288|
-
form
particles, which attract one
charged
oppositely
electrovalent bond leading to formation of an -electrovalent compound.
another to
an.
are
attraction betueen tuo oppositely charged ions
Bond ormation is due to Electrostaticforce of
-
xl+ yl-
Electrovalent or Ionic Compound
Anion
lonic bond
Cation
XY
Electrovalent or ionic bond
of one or more electrons from theThe chemical bond formed between two atoms by transfer
element
element to an-atom ofa norm-metallic electronegative
atom ofa metallic-electropositive
-
compound
|Electrovalent or ionic
formed as a
E B
from theresulf of transfer of one or more electrons element
The chemical compound
an -atom of a non-metallic- electronegative
atom ofa metallic- electropositiveelement to
Electrovalency
number
A
donatedor accepted by the valence shell ofan atom ofan
electrons
of
so as to achieve stable electronic configuration is called - electrovalency.
element-
The
valency
[Mg (28,2) loses 2electrons valency +2] [o(26) gains 2 electronsIONS-Xt or Yl-
ATOMS-X or Y'
Electrically -dharged particles (cations,
Electrically neutral particles
in solution.
May or may not exist independently. Exist independently
-
-
.Outermost shell - may or may not have
Outermost shell - have complete
duplet or octet.
duplet or octet.
REDUCTION -a process when
OXIDATION-a process whenAn atom or ion loses electrons
X-1e>X
or A2*-1e">A*
-
be. XXl+1e" or A2t A3* + le-]
Nal+
Na
Zn2+
Zn
S
Oxidation-Reductioie. Redox reactions
2FeClh
Cly
Cu
2Fe [oxidation] e
2C1
S
or
A3++1e-> A2*
2e
2C11
2e
Cu
Fe3++
Fe2+
2
s2
Cu
Zn
CuSOZSO4+
Cu
Zn+ Cu2
Zn2
Zn Zn2 [oxidation]e
2Fe2C
2Fe24.
Y
Y+1e
Fe3+
Fe2
2Fe2t
An atom or ion -gains electrons
Cu2
reduction] [+22
24
Cu
reduction |+2e
anions|
D.
compound- Sodium chloride
SODIUM CHLORIDE Formation
STRUCTURE
Of Electrovalent
sODIUM CHLORIDE - is formed as a result of - transfer of one valenceelectro
From metallic sodium atom
To
non-metallic chlorine atom
23
electronicconfiguration -2,8,1
Na
11[at. no.]
35
- electronic configuration - 2, 8,7
C
ATTAINMENT OF - Stable Electronic Configuration
soDIUM ATOM - attains stable electronic configuration of the nearest noble gas - Neon.
by losing one electron from its valence shell and becomes a positively charged
sodium ion [cation] - Nalt.
CHLORINE ATOM - attains stable electronic configuration of the nearest noble gas - Argon.
by accepting one electron in its valence shell and becomes a negatively charged
chloride ion [anion] C1-.
THE TWO OPPOSITELY CHARGED IONS - attract each other resulting in formation of the
electrovalent compound ie. sodium chloride - with an ionic bond.
Electronic Nearestnoble
Atom
configuration
To attain stable electronic
configuration of nearest noble gas
gas
|3Na [2,8,1]| Neon [281Atomlosesoneelectronfromitsvalenceshell.
SODIUM [metallic]
CHLORINE non-metali35a (287 Argoa123.8| Atomgainsoneelectroninitsvalenceshell
39K&35aform KCl and 23 Na& 321Sform NazS-both of whichare electrovalent compounds-
with an electrovalent or ionic bond.
FORMATION OF SODIUM CHLORIDE - Represented by electron dotstructure:
ELECTRON DOT STRUCTURE
Tonic equation
Na
latom]
le
Nal
[oxidation
cation]
Na ci: INal*. 1:ci:
[2,8
2.8,1]
reduction]
+le
atom
anion
N a +CI
atom
Nalt Cl
Sodium
chlorid
atom
NaSl
REFERENCE- Orbit structure
Na-atom
[28.71
Sodium Chlorine
(28,8
(28,7
[2.8,1]
NaCI
[Recap of std. IX]
Cl-atom
Before combination
Sodium atom [ Na]]
Chlorine atom [ CI ]
2,8,1
2,8,7
Nal+
Ci-
After combination
NaCl compound]
Sodium ion [ Nal]
2,8
25
Chloride tow[C1-]
2,8,8
Of Electrovalent compound-
STRUCTURE
is formed
-
oxide[Conts
ntd
Formation
II. CALCIUM OXIDE
CALCIUM OXIDE
Calcium
as a
result of
40
From metallic calcium atom
transfer of trwo
-
valence electrons
electronic configuration -2, 8, 8,.2
Ca
20at. no.]
16
To non-metallic oxygen atom
electronic configuration -2,6.
O
AITA
ATTAINMENT OF - Stable Electronic Configuration
CALCUM ATOM
by losing
-
attains stable
two electrons
calcium ion
[cation]
noble gas
electronic configuration of the nearest
from
its valence shell and becomes
a
-
Argon.
positively charged
Ca*.
-
of the nearest noble gas Neon.
attains stable electronic configuration
valence shell and becomes a negatively charged
accepting two electrons in its
by
oxide ion lanion] - O2-.
-
OXYGEN ATOM
THE TWO
-
each other resulting in formation
ie. calcum oide with an ionic bond.
OPPOSITELY CHARGED
electrovalent
compound
Electronic
IONS- attract
ofthe
To attain stable electronic
Nearest noble
configuration ofnearest noble gas
two electrons from its valence shell
420Ca [288,2 Argon [2,8,8]| Atom loses
Neon [28] Atomgains two electrons in its valence shell
[26]
Atom
configuration
CALCIUM [metallic]
gas
oxYGEN non-metallic] |1,0
FORMATION OF CALCIUM
structure:
oXIDE Represented by electron dot
ELECTRON DOT STRUCTURE
Iomic equation
Ca
atom]
2e
Ca2+
[oxidation
Ca: 1Ca
cation]
[2,88]
[2.8,8,2]
reduction]
o+2e
[anior
atom
Ca+O >Ca2* O2
Calcium
Calcium Oxygen
atom
oxide
atom
Cad
[Recap of std. IX]
REFERENCE- Orbit structure
Ca-atom
Cao
[2.8,82] (2,6]
[2.8]
(26]
1:o:
Ca**
O-atom
After combinatton UCaO
compound
Calcium ion [ Ca2]
Oide ion [O*]
Before combination
Calcium atom [Ca]
Oxygen atom [O]
2,8,8,2
2,6
O-
2,8,8
26
2,8
STRUCTURE-OfElectrovalentcompound--Magnesium chloride[Contd.
.
MAGNESIUM CHLORIDE Formation
MAGNESruM CHLORIDE
-
is formed
as a
result of
From one metallic magnesium atom 2412Mg
To two
-
transferoftwo valence electrons
electronic configuration -2,8,2
35
non-metallic chlorine atoms17CI
electronicconfiguration -2,8, 7.
ATTAINMENT OF - Stable Electronic Configuration
MAGNESTUIM ATOM - attains stable electronic configuration of the nearest noble gas- Neon.
by losing two electrons from its valence shell and becomes a positively charged
magnesium ion [cation] -
Mg2*.
CHLORINE ATOM- attains stable electronic configuration of the nearest noble gas - Argon.
by gaining one electron in its valence shell and becomes a negatively charged
chloride ion [anion] Cl
-
TRANSFER OF ELECTRONS - Magnesium atom donates two electrons [is oxidised],
whereas chlorine atom accepts only one electron lis reduced] to give chlorine ion.
Thus to acept the other electron donatedby Mg atom, there must be another 'C atom.
FORMATION OF COMPOUND - Therefore onemagnesium atom will combine with -
two chlorine atoms forming the elechrovalent compound - magnesium chloride.
FORMATION OF MAGNESIUM CHLORIDE- Represented by electron dot structure:
ELECTRON DOT STRUCTURE
Ionic equation
Mg
Mg2+
atom]
cation]
[28,2
[2,8]
2C1+2e
2CK
[oxidation
Mg
[reduction]
.ci:
[anion
atom
(2,8,7
[2.8,2]
[2,8,8]
Mg2Ci Mg2* 2Ci
[287
Magnesium Chlorine
MgC
REFERENCE Orbitstructure
Cl-atom
[Mg1 2ci>MgCl2
Mg-atomn
atom
atoms
Magnesium
chloride
[Recap of std. IX]
Cl-atom
Cl
Mg
After combination-MECl2 compound]
Before combination
Chlorine atom Magnesium atom Chlorine atom| Magnesium [ Mg*] Two chlortteigns [ 2C11-
2,8,7
2,8,2
2,8,7
2,8
27
2,8,8-2,,8
E. COVALENT BONDING
Covalent
compounds
Compounds
FORMATION OF- Covalent
electron pairsinvolves sharing
Formation
covalent compounds
atom-also
another
non-metalie
between one atom -generally non-metalic &
shared by the atom of each elementElectrons in valence shell are mutually
a stable electronic configuration.
such that each atom acquires
of
-
of
-
1-share onepair of electro
Non-metallic atoms-having7 valence electrons lor
-
xx
Non-metallic atom
Non-metallic atom
Covalent compound
oopai
single covalent bond]
One shared pair
(2,8] [28]
(2,7]
2.7]
-share
|Non-metallic atoms having 6 valence electrons
-
-
fwo pairs of electrons
(YY
Non-metallic atom
Non-metallic atoms- having 5 valence electronsNon-metallic atom
double - covalent bond]
[2.81 (2.8]
(26
2.6
Covalent compound
Two shared pairs
Non-metallic atom
share- three pairs ofelectrons
Covalent compound
[triple covalent bond
Non-metallic atom Three shared pairs
[28] [28]
[2,5
[2.5
electron pairs
Dissimilar non-metallic atoms form &ovalent molecules by sharing
-
-
A
B
Covalent compound
12) 2.8] 12 twosingle-covalentbonds
261
Covalent bond - The chemical bond -formed due to mutual sharing ofelectronsbetween the given pairs of atoms of non-metallic elements.
Bond formed by a shared pairofelectrons,each bondingatom contributing one electron to thepai
depending on no. of electron pairsshared: bond is single -L double [=) or triple (=] covalen
Covalent compound - The chemical compound -formed due tomutualsharingofelectrons
between the given pairs of atoms thereby forming a covalent bond between them.
Covalencyy
The number ofelectron pairs which an atom shares with one or more atoms
of the same or differernt kind to achieve stable electronic configuration is called covalency|
NON-POLAR COVALENTCOMPOUNDS POLAR COVALENT COMPOUNDS
Imp
Covalent compounds are said to be -
Covalent compounds are said to be
polar when shared pair of electrons are
nequallydistributed between the two atoms
-
non-polar when shared pair of electrons are -|
equally distributed between the two atoms.
No charge separation - takes place.
The covalent molecule is symmetrical and
- electrically neutral.
Charge separation
takes place.
The atom which attracts electrons mo
strongly develops a - slight negative char
-
8
e.g. H Cl O N, CH ca
eg H20, NH3, HCIH a
H-Cl
The covalent bond in which electrons are shared equally between the combining atoms
a non
polar covalent bond &when shared unequally is a polar covalent
bond.
28
F. STRUCTURE- Of Covalent compounds- Hydrogen, Chlorine
.
HYDROGEN- Non-polar covalent compound
Electronic
Atom
Nearest
To attain stable electronic
configuration noble gas
HYDROGEN H
configuration of nearest noble gas
Helium [2]
Hydrogen needs -one electron to attain stable duplet structure of nearest noble gas - Helium [2].
Each of the two'H'
atomscontributes one electron so as to have one shared pair of electrons
between them. Both atoms attain stable - duplet structure, resulting in the formation of a single covalent bond [H-H] between them.
FORMATION OF- HYDROGEN MOLECULE - Represented by electron dot structure
ELECTRON DOTSTRUCTURE
Before combination [H-atoms]
H
After combination [H2 -
H
H-atom
H:H
H-atom
REFERENCE Orbit structure
H atom
[H-H]
or
shared pair of electrons
Hydrogen molecule
Non-polar covalent compound
Electronic
Nearest
To attain stable electronic
configuration
noble gas
configuration of nearest noble gas
CHLORINE
H2
Single covalent bond
-
Recap of std. IX]
H atom
Il. CHLORINEAtom
One
molecule]
35,C1
[2,8.7]
Chlorine needs - one electron to attain stable -
Argon
[2,8,8]
octet structure of nearest noble
gas- Argon [2,8,8]
Each of the two 'CI atoms contributes one electron so as to have one shared pair of
electrons between them. Both atoms attain stable - octet structure, resulting in the -
formation of a
-
single covalent bond [Cl-ci]between them.
FORMATION OF - CHLORINE MOLECULE -Represented by electron dot structure:
ELECTRON DOT STRUCTURE
After combination
Before combination [Cl- atoms]
[Cl2 molecule]
-
C1:
CI
One shared
Cl-atom
Cl-atom
REFERENCE-Orbit structure
[Cl-c
-
IRecap of std. IX]
@
Cl atom
Cl atom
Chlorine molecule
29
Cl2
pair of electrons Single covalent bond
STRUCTURE Of Covalent compounds - Oxygen, Nitrogen [Cont-
Non-polar covalent compound
II. OXYGEN
Atom
Nearest
configuration
noble gas
configuration of nearestnoble gas
truwo electrons to attain stable
octet structure of nearest noble gas-Neon [28
Oxygen needs
Neon
16,0
2.6]
OXYGEN
Each of the
To attain stable electronic
Electronic
28
two'O'atomscontributes twoelectrons
-
pairs ofelectron
so as to have fwo shared
in the-
attain stable -octet structure, resulting
between them. Both atoms
between them.
double covalent bond. [O=OJ
rmation of a
-
FORMATION OF
-
Represented by electron dotstructure:
OXYGEN MOLECULE
ELECTRON DOT STRUCTURE
After combination [O2 -
molecule
Before combination [O-atoms]
:0:0:
:0
Two shared pair of electrons
O-atom
O-atom
covalentbond
SERIES
(O
Oxygen molecule
O atom
O atom
Non-polar coyalent compoundd
-
Electronic
configuration
Atom
[O
O]
Double
[Recap of std. IX]
REFERENCE - Orbitstructure
IV. NITROGEN
-
To attain stable electronic
noble gas
configuration of nearest
Nearest
noble gas
to attain stableNitrogen needs three electrons
Neon
Neon
NITROGEN 14, N
[2.5]
-
octet structure
[28]
of nearestnoble gas
(28
-
electrons so as to have three sharedpair ofelectrons
Each ofthetwo Natoms contributes 3
octet structure, resulting in the
between them. Both atoms attain stable
between them.
formation of a triple covalent bond. [ N=N]
MOLECULE Represented by electron dot structure
FORMATION OF NITROGEN
-
-
-
-
-
ELECTRON DOTSTRUCTURE
After combination [Na molecule]
-
Before combination [N - atoms]
N
N
N
N-atom
N atom
N=N
ofeach
12 electrons in the outer
are not involved in sharing, duringformation of N2
TRecap of std. IX]
Nitrogen molecule
Natom
30
> N
cooalent bond
Three shared pair of electrons-Triple
shell
nitrogen atom
N-atom
REFEREACE- Orbit structure
N:
lel
STRUCTURE-Of Covalent compounds-Carbon tetrachloride, Methane
V.
CARBON TETRACHLORIDE Non-polar covalent compound
Atom
CARBON
CHLORINNE
| Electronic
Nearest
To attain stable electronic
configuration noble gas
12
6C2,4
configuration ofnearest noblegas
| Neon [2,8] Carbonneeds-fourelectronsto attain- stableoctet.
7l28,7]| Argon [2,8,8] Chlorineneeds-oneelectronto attain-stableoctet.
One atom of carbon - shares four electron pairs - one with each of the four atoms of chlorine.
FORMATION OF-CARBONTETRACHLORIDEMOLECULE- Represented by
ELECTRON DOTSTRUuCTURE
Before combination [4 [CI] and 1 [C] atom]
electron dot structure
After combination [cCl4- molecule]
ci
CI
:ci:
C1-C-CI
:ci+* C *+ Ci:
CC4
CI
:CI
REFERENCE- Orbit structure
Four single-
C
covalent bonds
[Recap ofstd. IX]
Oetom
Cl-atom
Cl-atom
O)Cl-atom
VI. METHANE
Atom
Carbon
EN
tetrachloride
moleculee
L
Non-polar covalent compound
Electronic
configuration
Nearest
To attain stable electronic
noble gas
configuration of nearestnoble gas
CARBON 12C
Neon
[2,8] Carbonneeds-fourelectrons toattain- stable octet.
[24]|
HYDROGEN
(1] Helium [2]
to attain-stableduplet.
One atom of carbon shares four electron pairs one with each of the
atoms
|Hydrogenneeds-oneelectron
-
four
-
of hydrogen.
FORMATION OF - METHANE MOLECULE - Represented by electron dot structure:
ELECTRON DOT STRUCTURE
Before combination [4 [H] and 1 [C] atom
H
H+x
x+H
After combination [CH4- methane molecule]
H
HCH
or
H-¢H
H
Four single Covalent bonds
H
REFERENCE- Orbit structure
[Recap of std. IA
( HH-atom
H-atom
(
H-atom
H-atom
31
STRUCTURE- Of Covalent compounds - Water, Ammonia [Contd
VII. WATER-Polar covalentcompound
Atom
Electronic
configuration
To attain stable electronic
Nearest
configuration of nearest noble gas
moble gas
Helium [2] Hydrogenneeds-oneelectrontoattain-stabledunl
1H [1]
OXYGEN 160
[2,61 Neon [2,8] Oxygenneeds-rwoelectronstoattain-stableocte
with the oxygen atom
Each of the two hydrogen atoms shares an electron pair
such that hydrogen acquires a - duplet configuration and oxygen an octet configuration
HYDROGEN
-
resulting in formation of- fwo single covalent
bonds
[H-O-H] in the molecule of water
FORMATION OF - WATER MOLECULE- Represented by electron dot structure:
ELECTRON DOTSTRUCTURE
Before combination [2H and 1[0] atom]
HOH
xH
Hx
|REFERENCE - Orbitstructure
H-O-H
or
> H,o
Two single - covalent bonds
H-atom
O-atom
H-atom
After combination [Watermolecule
[Recap of std. IX]
fLone pair of electrons
FLone pair of electrons
O atom
H atom
Water molecule
H atom
VIII. AMMONIA Polar covalent ompound
Nearest
Electronic
Atom
NITROGEN 1N (2,5] | Neon
HDROGENH
To attain stable electronic
configuration of nearest noble gas
configuration noble gas
2,8]| Nitrogenneeds-threeelectronstoattain-stableoctet
[1] | Helium [2] Hydrogenneeds-omeelectrontoattain-stableduplet
One atom of nitrogen shares three electron pairs one with each of the three atoms ofhydrogen.
FORMATIONOF -AMMONIAMOLECuLE-Representedbyelectron dotstructure
e
ELECTRON DOTSTRUCTURE
Before combination [ 3 [H] and 1 [N] atom]| After combination [NH,- ammonia molecule
H
H
H
H+xNx+H
Nx H
lone pair]1
REFERENCE- Orbitstructure
Oor
H-N-H
Three single
covalent bonds
[Recap of std. IX]
(Hatom
H-atom
(o
H-atom
32
o)
electrons
FLonepai df
RDINATE
G. COOR
BOND-Formation of Ha0+ & NH4
ion
THE LONE PAIR EFFECT-Ofoxygen atom of Water &nitrogen atom of Ammoni
.FORMATION
Of Water Molecuie - Lone pair effect of the oxygen atom ofwatermoe
IN THE MOLECULE OF WATER
H
9 + xH
Oxygen atom has-
WATER
MOLECULE
MO
Hx
.Twolone pairs ofelectrons.
FORMATION-Of AmmoniaMolecule-Lonepaireffectofthenitrogenatomofammoniamolecule
H
IN THE MOLECULE OF AMMONIA
H
X
Hx+ N
xH
HN<H
AMMONIA
Nitrogen atom has
MOLECULE
One lone pair of electrons.
Lone pair ofelectrons-are a pair of electrons not shared with any other
FORMATION
O f Hydronium ion [ H O *
&
Hydroxyl [OHF ions - In water
NH
H
H
X
+
HxO
Hl HxQ:H
lone pair
Water molecule
HO
From acid
Addition of acid
H
Water molecule HYDROKL ION
HO
HO
H
Hx
orH-HH0
lone pair
HYDRONIUM ION
Hydrogen ion
aton
OH-
Hl+
Hydroxyl ion the acid
Hydronium ion (stable positiveion
to water [polar solvent] results in release of hydrogen ion [H]from
[HCI-polar covalent]
o
Chloride
H*
Hydrogen ion
Water (
Cl
Chloride ion
Hydrogen
In water- the 'O' atom contains two lone pairs ofelectrons after completing its octet
The hydrogen ion - accepts one lone pair of electrons of the oxygen atom of water mnol
ecule leading to formation of a coordinate covalent bond. F6>H]
FORMATION- O f Ammonium ion - N H
H
H
H NO
or
H-NH
Ammonia molecule
+OHl-
H
H
H
NH3
Ammonia gas
HN:H
+Hl+
AMMONIUM ION
Hydrogen ion
NH 1+
Hl+
Ammonium ion
From water molecule
+
H
Hydroxyl ion
NH OH
Ammonia dissolves in water [polar solvent] leading to formation of ammonium ion.
In ammoni
- the 'N atom contains one lone pair of electrons after completing its octet.
The hydrogen ion - from water accepts the lone pair of electrons of the nitrogen
atom of ammonia molecule,leading to formation ofa coordinate covalent bond FN>H]
COORDINATE BOND
the shared electrons
which involvesoneofthe combiningatomscontributingbothof
Typeofoovalency
ie. a bond formed by a shared pair of electrons With both electrons comingfrom the samne atom.
[It has properties of both ionic &k covalent bonds &e 1s also called as- dative ar co-ionic bond.] Compounds containing
Electrovalent & Covalent bond: Na[OH, CaCO
INaOH
lonic, covalent
coordinate bond-
Caualent
Coordinate bond:CE O, [H-O-N=O1
H
NHCl ie.H-NHC, K [Fe(CN)%
33 mPR
lcoj
HUNO
H.
PROPERTIES&COMPARISON-Electrovalent
&Covalent compound
COVALENT
COMPOUNDS
ELECTROVALENT [IONIC] COMPOUNDS
Inp
m
1.STATE Bonding
-
-
1.STATE- Bonding-
electrovalent
covalent
Existence -Gases, liquids or softsolids,
Existence - Crystalinehard solids (rom temp| Constituent
Units Molecules
Constituent Units - Ions(metallic, non-metallic] Force of attraction - Weak
Force o f attraction - Sfrong
Van der Waal'sforces exist between -molecules
ions.
Electrostatic forces exist
REASON: lons [chargedparticles whichattract
between
one
another
REASON: Molecules have weak forces of
attraction between them & hence covalent
to form electrovalent compounds] -|
compounds are gaseousif molecules are less
are closelypackedwith strongforceofattraction
solids.
hence ionic compounds are hard
& liquid or soft solids [if molecules are more
-
2.VOLATILITY
| 2. VOLATILITY
Volatile
Non-volatile
& BOILING POINT
3. MELTING
Low melting point and low boiling point
3. MELTING & BOILING POINT
melting point and high boiling point.
High
REASON:Strongelectrostatic force of attraction
between ions. Large amount of energy
REASON:Weak Vander Waalsforceofattraction
between molecules. Less amount of energyrequired to break the force of attraction.
-
required
to break the
force of attraction.
4.CONDUCTION OF HEAT
4.CONDUCTION OF HEAT
Bad or non-conductors
Good- conductors of heat
5.CONDUCTION OF ELECTRICITY
Gaseous or liquid state -Non-conductors
Solid state -Non-conductors
Molten or aq. soln. state - Good conductors
Soft solid state - Non-conductors
REASON: Strong electrostatic force keeps
ions in fixed position in the - solid state,
The force is weakened in the molten state &
disappears in soln. state, hencefreeionsformed
migrate to - oppositely charged électrodes.
Can-be electrolysed in molten/aq. soln. state.
On electrolysis the ions being charged are
attracted towards the respective electrodes.
CC contain molecules & not free ions, hene
are non-conductors. Polar covalent
compounds e.g. HC, NH3 show charge
separation& dissociate in HO[polar solvent)
Cannot - be electrolysed in normal state.
In soln. state, polar covalent compounds
undergo electrolysis. e.g. HCI & NH3 gas.
7.SOLUBILITY
7.SOLUBILITY
Soluble in organicsolvents [non-polar
Insoluble - in water [polar]
-
REASON: Water Ipolar solvent] has a
dielectric constant ie. capacity to weaken the
high
force of attraction, thus resulting in free ions.
Organicsolvents (non-polar) have low dielectric
constants and do not cause dissolution
8.REACTIONS
.Undergo - high speed ionic reactions.
REASON;: Free ions easily formed in solution,
rapidly regroup in solution.
-
9.DISSOCIATION
REASON: Organic solvents [non-polar
e.g. benzene, alcohol, dissolve non-polar
covalent compounds [like dissolves like!
Water(polarsolvent] cannotdissolvenon-polar
covalent compounds, but dissolves polar
8. REACTIONS
Undergo -slow speed molecular reactioIS.
REASON: Covalent molecules are fir
broken & new bonds are - slowBy establishea.
9.1ONISATION
.Undergoesionisation
Undergoes electrolytic dissociation
on passage of electric current.
in solution state on passage of electriccurren
Process involves formation of ion>
Process involves separation of ions
-
already present in the ionic compound.
e.g. NaCl
REASON: Non-polar covalent compounds e g
6. ELECTROLYSIS
6. ELECTROLYSIS
Soluble - in water
Insoluble in organicsolvents.
of heat
5.CONDUCTION OF ELECTRICITY
from molecules which are not in ionic state
Nal+ CIllin molten state]
34
e.g.
HCI
H+CI1-[in solution state