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Chemical Bonding
A Force that acts (^) b/w two or more atoms to (^) hold them together
characteristics of Ionic compounds
as a stable molecule is known as chemical (^) Bond (^). Reason -^ a)^ Hard^ crystalline^ solid a) To^ attain^ stability b) To Follow^ octet Rule (^).
b) High MP/ BP
stability ✗^1
Energy
4 Highly soluble^ in^ polar solvent. 114201
Ionic Bond :^ / ElectroValent Bond 1 covalent Bond :
Electrostatic attraction b/w cation and anion .^ Bond^ formed^ by mutual^ shaving of^ electrons^ between
Metal + Non - metal combining atoms^.
Cation +^ Anion^ H^
• → H :O : = :O :
Electro (^) valency : Bond pair
- pair of^ election^ participating in^ Bonding. Charge on^ cation^ or^ anion^ in^ Ionic^ Bond^.^ Lone^ pair - pair of^ election^ not^ participating in^ Bonding.
NaCl Electrovalency of Na =^ -
Coval ency :
Electrovalency of Ct =^ -
No.^ of^ Bonds formed by an atom in a covalent Bond .
Favourable conditions^ for ionic Bonding :
' (^) Coval
ency =3^ a -41 ,^ Coval^ ency
= (^5)
a) Low ionisation energy of metal .
μ
- F'
μ
a- F-^
"
b) High election gain enthalpy. H
Cl c) (^) High Lattice (^) energy 1 Force of attraction ) co -^ ordinate^ Bond : lattice energy :
special type of^ covalent^ Bond^ in^ which^ Both^ the^ electrons
Amount of
energy released^ when^ one^ mole^ of^ crystal^ lattice^ are given by one atom and accepted
By another^. is (^) formed (^). H (^) - H
Lattice
energy depends^ on^
- H - N : (^) + H+ → (^) H - N :→ H H
' f
a) Charge LE^ ✗ Charge b)^ Size^ of^ atoms^ -^ LE^ ✗^1
H " co -^ ordinate^ Bond size
variable Coval
ency :
Born - Haber cycle :
Deals with the energy changes involved in Formation No^.^ Of^ Bonds^ =^ No^.^ of^ unpaired elections.
of one mole^ of^ ionic crystal. Only valence electron participate in
Bonding.
Na (^) is) +
f-
Clz AH^ Formation^ , NaCl e. g. 502 5 =^ [^ Ne^ ]^ 3s ' 3ps 3d ^ Tt t t t t (^) 1st
excited
AH (^) sub^ 1-2^ HBDE (^4) unpaired electron =^4 Bond (^). state
Ning,^ ciig,^ LE
Drawbacks of octet rule IEI Aeg Hi
a) electron^ deficient^ molecules^ (^ Hypovalent^ )
Niicg,^ ciig, e.
g.
131=3 and Beck
AH formation = AH sub -1^ IE , +
AHBDE + Aeg H^ , +^ LE^ b)^ Expansion of^ octet^1 Hyper valent^ ) e. (^) g. PC^ Is and^503
Why
to study Boon - Haber?
Because (^) we cannot determine (^) value of LE
experimentally
c) Odd^ election^ species. e. g. NO^2
Bond Parameters - Overlapping :
a) Bond^ order^11301 a)^ +^ ve^ overlapping
Number (^) of Bonds between two combining atoms^.
Same sign lobes overlap.
H - H B. 0=1 Bond^ is^ Formed^. 03 B-^ 0=1. C - C B. 0= Colts B. 0=1.
} Due^ to b) - ve
overlapping c=C B. 0=2 Resonance opposite sign lobes^ overlap. C. =^ C^ B-^ 0=3^ No Bond Formation . b) Bond^ length 11311 c) Zero overlapping. Px (^) PY z-axis
Distance b/w nucleus of two atoms effective
overlapping zero^.^8
No Bond Formation (^).^ Px^ +^ Py c) Bond^ energy 1 BE^ )
overlapping orbital^
to (^) nucleus (^). Energy (^) required to^ dissociate^ any Bond^. more extent of
overlapping
and
stronger
is bond .
BL ✗^ Size of^ atoms ✗^1 IS^
- IS > (^) 25-25 > (^) 35- No.^ of^ Bonds
- Move the directional nature (^) of
overlapping
orbitals
B. L - H - F <^ H - CI <^ H - Br <^ H - I
move is^ the^ extent^ of^ overlapping.
B. L - C - C >^ c=c >^ CEC 25-25 <^25 - 2p < 2p - 2p
1. 54 Ñ^ 1.34 Ñ^ 1.2 Ñ^
Axial (^) overlapping or End to End (^) Overlapping :
B. E^ ✗^ NO^ -^ Of^ Bonds^ ✗^ Overlapping^ along^ inter^ nuclear^ axis^.
gizefatom -
Sigma Bond^ is^ Formed^.
B. E - H -^ F^ >^ H - CI >^ H - Br >^ H - I -^ S^ -^ orbital^ always (^) undergo axial^ overlapping. B. E - C - C <^ C=c N - N >^ O_O >^ F- F Lateral
overlapping or^ sideways^ overlapping.
B. E- CI - CI >^ Bo - Bo >^ F - F >^ I- I (^) - Overlapping above^ and^ below^ inter
- nuclear axis (^). B. E - S - s >^ O - O - TI - Bond (^) is Formed (^).
d) Bond angle 1 Hybridisation ) -^ First^ Bond^ Formed^ is^ always o^.
Angle b/w^ two^ adjacent Bonds^. Difference between^ Sigma and^ pi Bond^ :
valence (^) Bond theory 11113T)^ Sigma Bond^ Pi^ Bond
stronger the^ covalent^ Bond^ it^ Formed^ by axial^ overlapping it^ Formed^ by parallel overlapping
t'
2) stronger Because^ extent^ of^ 2) Weaker^ because^ extent^ of
More is^ B.^ E
y, overlapping is^ move^. overlapping
is less (^). Less is (^) B. L (^) 3) Allowed^
overlapping
S - S , S - p. 3) Allowed
overlapping p
and p - p. and d- d.
41 Free Rotation (^) possible.^41 Free^ rotation^ not^ possible
Dipole moment^ (^ μ^ )^
: Drawbacks^ of^ VBT^ :
al According to^ VBT^. Oxygen molecule^ was^ Diamagnetic
I 1
⑦ a^ d^ so^ M=^9 ✗^ d^ But in practical , it was formed to be
9 9 paramagnetic
61 Fractional Bond order (^) was not (^) explained. Vector (^) quantity :^ I +^ veto - vet c) (^) stability of^ molecule^ was not^ decided^ by VBT.
( less^ EN^ to^ More^ EN^ )
H - Cl (^) μ-1-0 -^ Main^ points of^ MOT^ :
CI - CI μ=o a)^ In^ atoms^ ,^ electrons^ are^ present in^ atomic^ orbitals
Move the EN (^) , more is (^) dipole moment (^).^ b)^ In^ molecules^ ,^ electrons^ are^ present in^ molecular^ orbitals^. μ =^ H^
- F > (^) H - a > (^) H - Bo > (^) H - I c) NO^.^ of^ molecular^ orbitals^ =^ Number^ of^ atomic^ orbitals^ combined^.
= (^) c- Cl > (^) C - F > (^) c- By > (^) c- I When^ two^ atomic^ orbitals^ combine^ =^2 molecular^ orbitals μ = cclq <^ CHC^13 <^ ctlzclz^ <^ ctlzcl^ are Formed^. a) (^) Bonding molecular^ orbital^ (^ BMO^ ) μ = (^) NH 3 > (^) NF (^3) b) Anti^ - Bonding molecular^ oobital^ (^ ABMO^ ) Application of^ Dipole^ moment^ : MO^ is^ under^ the^ influence^ of^ two^ or^ more^ than^ two^ nuclei^.
Electrons are Filled according to Afbau'S Rule . Hund 's
1) To determine^ whether^ a^ molecule^ is^ polar 00 Rule^ of^ Max. multiplicity and^ pauli's^ exclusion^ principle.
non polar.^ MO^ are^ formed^ by Linear^ combination^ of^ atomic^ orbitals^.
21 TO^ Find^ %^ ionic^ character^ in^ covalent^ Bond^. A (^) and B LCAO
YA YB YBMO^ =^ YA^ -1^ YB^ constructive^ interference
% ionic character = Experimental μ ✗ too YABMO^ =^ YA^ -^ YB^ Destructive^ interference
Theoretical μ YMO^
= YA -1-
Fagan 's^ Rule^ : BMO^1 Bonding Molecular orbital^1
TO Find covalent character in Ionic^ Bond.^ Formed^ by^ constructive^ interference^.
Covalent character ✗ Polarisation (^).
Lower energy and more stability.
-^ Increases^ electron^ density in^ region b/w^2 nuclei Factors (^) affecting polarisation : may or (^) may not
a) Size^ -^ For^ Max.^ covalent^ character^ YBMO = YA +^ YB
have node (^).
Cation size should be small 4213170 =^ YA
'
Anion size should be large. ABMO ( Anti -
Bonding
Molecular orbital 1 Lid >^ NaCl >^ KCI >^ Rbcl >^ Cscl (^) Formed by destructive^ interference^.
b) charge Higher energy and less^ stability.
For (^) Max. covalent character Electron density decreases^ b/w^2 nuclei^.
Charge on^ cation^ and^ anion^ should^ be^ more^.
YABMO =^ YA - YB
NaCl < Mgclz <^ Along <^ siclq 42ABMO =^ 42A^ -1473^ -^ 24A^413
c) Electronic^ configuration of^ cation^.
Formal
charge
cations
having pseudo^ noble^ gas configuration F.^ c^ =^ Valence^ e-^ -^ [^ Non^ - Bonding e-^ ]^ -
12-1 Bonding^
e- 1 has (^) more covalent character (^). CH} -^ O^ -^ CH} 5=6-[3+2] CUCI >^ NaCl
Types
of Molecular orbital^ :
at GMO^ -^ Formed^ by overlapping along internuclear^ axis^.
- (^) IS 615 625 625 021oz 6* BMO ABMO BMO ABMO BMO ABMO
b) TIMO^ - Overlapping is^ above^ and^ below^ inter^ -^ nuclear^ axis
-112Pa IT^
2Pac TT2Py lT*2Py
Electronic
configuration
of (^) molecules :
case 1 :^ No. of e- £ 14 (
Tl2Px=T12Py)o2Pz
case 2 :^ No - of e- >^14
o2Pz(TT2Px=T12Py
Na= No. of e- in ABMO
Nb= No. of e- in BMO
B.
ING -^ Na^ )^ Trick
B- 0>0 →^ molecule exists toe^
B. 010 →^ molecule does not exist . He
stability
of (^) molecule ☐ e- →^ B. 0= 13 e- →^ B. 0=2. move the^ 13^0^ = move is^
stability.
14 e- →^ B. 0= If B. 0 is^ same (^) , then lower^ hoof^ e- is ABMO (^) '
☒ e- →^ B. 0=2.
Higher
is
stability.
16 e-^ →^ B.^ 0=
B. 0 ✗ B. Ex -
Me
B. 0=1.
B. L
18 e- →^ B. 0=
Diamagnetic
unpaired e- Exception - co -1=13^ e-
Paramagnetic
unpaired e-^.^ B.^ 0=3.
