Valence shell electron pair repulsion theory (VSEPR THEORY)
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The document outlines Valence Shell Electron Pair Repulsion (VSEPR) theory, which explains how the spatial arrangement of electron pairs around a central atom affects molecular shape. It highlights key postulates, including the impact of lone pairs and bond pairs on molecular geometry and individual bond repulsion strengths. The document also discusses the influence of electronegativity on bond angles and provides references for further reading.
![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.](https://image.slidesharecdn.com/valenceshellelectronpairrepulsiontheory-170524112504/85/Valence-shell-electron-pair-repulsion-theory-VSEPR-THEORY-5-320.jpg)
![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](https://image.slidesharecdn.com/valenceshellelectronpairrepulsiontheory-170524112504/85/Valence-shell-electron-pair-repulsion-theory-VSEPR-THEORY-10-320.jpg)
Valence shell electron pair repulsion theory (VSEPR THEORY)
- 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
- 12. SHAPE OF MOLECULES CONTAINING lp & bp
- 15. REFERENCES • J.D Lee, WILEY INDIA EDITION, Concise Inorganic, Vol. 5 @ Pg. 74-80. • Atkins, Rourke, Weller & Armstrong. Shriver & Atkins, OXFORD South Asia edition, Inorganic Chemistry, Vol. 5. Topic 2.3 @ Pg. 36-39. • Pictures From www.oxfordtextbooks.co.uk/orc/ichem5e/ • Pictures from Wikipedia- free encyclopedia- www. Wikipedia.org.
- 16. THANKS TO RESPECTED TEACHERS AND STUDENTS THEEND