Designed in a very easy manner so that u all are able to understand each and everything easily.
Gillespie & Nyholm proposed this theory ion 1957 and its is based on the direction of bonds in a polyatomic molecule.
Based on this there are several postulate that are very necessary to know before any molecule to study.
Analytical Profile of Coleus Forskohlii | Forskolin .pptx
Valence shell electron pair repulsion theory (VSEPR THEORY)
1.
2. VALENCE SHELL ELECTRON PAIR
REPULSION THEORY
PRESENTED
BY
ALTAMAS ALI
B.Sc – MICROBIOLOGY
SEM. – 2ND
SCHOOL OF LIFE AND ALLIED
HEALTH SCIENCE
THE GLOCAL UNIVERSITY
3. CONTENTS
• ABBREVIATION USED
• INTRODUCTION
• VSEPR THEORY : MAIN POSTULATES OF VSEPR
• REPULSION STRENGTHS
• CAUSE OF ALTERNATION IN SHAPE
• EFFCT OF ELECTRONEGATIVITY
• SHAPE OF MOLECULES CONTAINING lp & bp
• REFERENCES
4. ABBREVIATION USED
• VSEPR THEORY – VALENCE SHARE ELECTRON PAIR REPULSION
THEORY
• lp – lone pair
• bp - bond pair
• max. – maximum
• min. - minimum
5. INTRODUCTION
• VSEPR theory was suggested by Sidgwick and Powell [1940]
• It was further improved by Gillespie and Nyholm in 1957.
• Based on that in a polyatomic molecule the direction bonds around the
central atom depends on the total number of bonding &non-bonding
electron pairs in its valance shell.
6. VSEPR THEORY
MAIN POSTULATES OF VSEPR :
• The shape of the molecule is determined by repulsions between all
of the electron present in the valance shell.
• Electron pairs in the valence shell of the central atom repel each
other and align themselves to minimize this repulsion.
7. • Lone pair electrons takes up more space round the central
atom than a bond pair.
• Lone pair attracted to one nucleus, but bond pair is shared by
two nuclei.
• The minimum repulsions to the state minimum energy and
maximum stability of the molecule.
8. REPULSION STRENGTHS
• Lone pair -Lone pair Lone pair -Bond pair
Bond pair-Bond pair
• Triple bond >double bond >single bond
9. CAUSE OF ALTERNATION IN
SHAPE
• Presence of lone pairs on the central atom causes slight
distortion of the bond angles from the ideal shape.
• The magnitude of repulsions between bonding pairs of
electrons depends on the electronegativity difference
between the central atom & the other atoms .
10. EFFCT OF ELECTRONEGATIVITY
Five electrons in the valance shell of
Nitrogen. [1s2 2s2 2p3]
Molecular geometry- Tetrahedral [e-pairs arrangement]
or Trigonal Pyramidal [VSEPR]
Presence of lone pair causes slight distortion from 109⁰28′ to 107⁰48′ to 102⁰30′
Repulsion between bondpair-bondpair is less in NF3 than in NH3
11. Valence Electron Pair
Geometry
Number of
Orbitals
Hybrid
Orbitals
Linear 2 sp
Trigonal Planar 3 sp2
Tetrahedral 4 sp3
Trigonal Bipyramidal 5 sp3d
Octahedral 6 sp3d2