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Chemical Bonding

  • Valence Bond Theory

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  • Shapes of different orbits

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Shape of s-orbit

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Shapes of p-orbits

px py pz

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Shapes of d orbitals---�

dxy

dyz

dxz

dx2-y2

dz2

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Covalent bond-

A bond formed by sharing of electron pair between combining atoms in a molecule is called covalent bond

H2 ---- H : H Cl2 ---- Cl : Cl

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H( z =1) --- 1s1 Cl (z= 17) --- 1s2 2s2 2p6 3s2 3p5

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  • Be (z= 4) 1s2 2s2 -----------------
  • B (z=5) 1s2 2s2 2p1-----------------
  • Si (z=14) 1s2 2s2 2p6 3s2 3p2 --
  • P (z=15) 1s2 2s2 2p6 3s2 3p3 ----
  • S (z=16) 1s2 2s2 2p6 3s2 3p4 ----

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2s 2p

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  • Be (z= 4) 1s2 2s2 ----- is zero valent
  • B (z=5) 1s2 2s2 2p1-------is monovalent
  • Si (z=14) 1s2 2s2 2p6 3s2 3p2 ------ is divalent
  • P (z=15) 1s2 2s2 2p6 3s2 3p3 ------is trivalent
  • S (z=16) 1s2 2s2 2p6 3s2 3p4 ----is divalent

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From ground state electronic configuration of Be it is zero valent but

in BeCl2 it is divalent.

From ground state electronic configuration of B it is mono valent but

in BF3 it is tr ivalent.

From ground state electronic configuration of Si it is di valent but

in SiCl4 it is tetra valent.

From ground state electronic configuration of P it is tri valent but

in PCl5 it is penta valent.

From ground state electronic configuration of S it is divalent but in

SF6 it is hexa valent.

Concept and need of Hybridisation

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Formation of BeCl2

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2s 2p

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sp hybridisation

Ground state of Be

Exited state of Be

Formation of BeCl2

X

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Electron of Be & X electron of Cl

Be(z= 4)

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1s2 2s2 -- is zero valent

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Linear geometry

Be

2 sp hybrid orbits of Be

Angle is 180 degree

Cl

Cl- px orbit with

single electron

Cl

Cl- px orbit with

single electron

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Linear geometry

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Hybridisation

  • The phenomenon of mixing and recasting of the atomic orbitals having comparable energy of an isolated gaseous atom to form set of new equivalent orbitals is called hybridization.

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Formation of BF3

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2s 2p

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sp2 hybridisation

Ground state of B

Exited state of B

Formation of BF3

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X

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Electron of B &

X electron of F

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B(z=5)

1s2 2s2 2p1-------is monovalent

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Trigonal geometry

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B

F

F

F

1200

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Formation of SiCl4

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3s 3p

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sp3 hybridisation

Ground state of Si

Exited state of Si

Formation of SiCl4

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Electron of Si &

X electron of Cl

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Si(z=14)

1s2 2s2 2p6 3s2 3p2 ------ is divalent

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Tetrahedral geometry

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Si

Cl

Cl

Cl

Cl

109.50

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Formation of PCl5

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3s 3p 3d

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Sp3 d hybridisation

Ground state of P

Exited state of P

Formation of PCl5

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Electron of P

& X electron of Cl

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P(z=15)

1s2 2s2 2p6 3s2 3p3 ------is trivalent

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Trigonal bipyramidal geometry

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P

Cl

Cl

Cl

Cl

Cl

Equatorial Bond

Axial Bond

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Formation of SF6

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3s 3p 3d

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sp3d2 hybridisation

Ground state of S

Exited state of S

Formation of SF6

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Electron of S

& X electron of Cl

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S(z=16)

1s2 2s2 2p6 3s2 3p4 ----is divalent

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Octahedral geometry

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S

F

F

F

F

F

F

Equatorial Bond

Axial Bond

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Formation of IF7

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5s 5p 5d

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Sp3d3 hybridisation

Ground state of I

Exited state of I

Formation of IF7

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Example

Hybridization

Angle

Geometry

BeCl2

sp

1800

Linear

BeF3

sp2

1200

Trigonal planer

SiCl 4

sp3

1090

Tetrahedral

PCl 5

sp3d

1200 & 900

Trigonal bipyramidal

SF6

Sp3d2

900 & 900

Octahedral

IF6

Sp3d3

900 & 720

Pentagonal bipyramidal

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Thank you

B. S. Kadwale Dept of Chemistry Ajara Mahavidyalaya Ajara