Shapes Of And Bond Angles In Simple Molecules


Published on

1 Comment
No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

Shapes Of And Bond Angles In Simple Molecules

  1. 1. Shapes of and Bond Angles in Simple Molecules
  2. 2. Introduction <ul><li>In molecules there are 2 types of electron </li></ul><ul><li>1. Bonding Pairs </li></ul><ul><li>2. Non-bonding or lone pairs </li></ul>
  3. 3. <ul><li>pi - bonds have a very limited impact on shape. sigma-bonds have a much more important effect. </li></ul>
  4. 4. <ul><li>Ionic bonds - non-directional </li></ul><ul><li>Covalent bonds – have preferred direction in space </li></ul><ul><li>All covalent compounds have a particular shape </li></ul><ul><li>As a result of spatial distribution of orbitals. </li></ul>
  5. 5. VSEPR Theory <ul><li>Predict the shapes and bond angles of molecules and molecular ions </li></ul><ul><li>pairs of electrons that surround the central atom of a molecule or ion are arranged as far apart as possible to minimize electron-electron repulsion. </li></ul>
  6. 6. VSEPR Theory <ul><li>The idea can be used to predict the shapes of molecules by following a simple procedure: </li></ul>
  7. 7. VSEPR Theory <ul><li>Decide which is the central atom in a molecule. </li></ul><ul><li>In cases of ambiguity, pick the least electronegative atom as this atom will be better able to share its electrons with the other atoms in the molecule. </li></ul>
  8. 8. VSEPR Theory <ul><li>Count up the valence (outer shell) electrons on the central atom. </li></ul><ul><li>Count up the electrons used by the outer atoms to make bonds with the cental atom. </li></ul>
  9. 9. VSEPR Theory <ul><li>The sum of ( 2 ) + ( 3 ) divided by two gives the Valence Shell Electron Pair (VSEP) count. </li></ul><ul><li>The predicted geometry of the molecule is based on the number of VSEP. </li></ul><ul><li>i.e. the arrangement of EP around the central atom (both lone pair and bonded pair). </li></ul>
  10. 10. VSEPR Theory <ul><li>Electrostatic force of repulsion between electron pair. </li></ul><ul><li>Repulsion- to attain most comfortable arrangement. </li></ul><ul><li>Each atom wants an octet of electrons. </li></ul>
  11. 11. Types of Repulsion <ul><li>Bonding pair- Bonding pair </li></ul><ul><li>Lone pair-bond pair </li></ul><ul><li>Lone pair- lone pair </li></ul>
  12. 12. Strength of Repulsion <ul><li>Depends on proximity of electron pairs to central atom </li></ul><ul><li>Lone pairs closer to central atom- they are delocalized- have no other nucleus to attract them </li></ul><ul><li>Bond pairs –attracted to another nucleus </li></ul>
  13. 13. Strength of Repulsion <ul><li>Lone pair- Lone pair repulsion > Lone pair- Bond pair repulsion > Bond pair- Bond pair repulsion </li></ul>
  14. 14. Effect of Strength <ul><li>Lone pairs push bond pairs closer </li></ul><ul><li>Smaller angles result </li></ul>
  15. 15. Shapes of Molecules
  16. 16. Linear <ul><li>2 bonded pairs </li></ul><ul><li>0 lone pairs </li></ul><ul><li>Bond angle of 180 </li></ul><ul><li>Examples;BeCl2, CO2, HCN, C2H2 </li></ul>
  17. 18. Trigonal Planar <ul><li>3 bonding pairs </li></ul><ul><li>0lone pairs </li></ul><ul><li>Bond angle of 120 </li></ul><ul><li>Examples; BF3, SO3, NO3-, CO32-, C2H4 </li></ul>
  18. 21. Tetrahedral <ul><li>4 bonding pairs </li></ul><ul><li>0 lone pairs </li></ul><ul><li>Bond angle of 109.5 </li></ul><ul><li>Examples; NH4+, SO42-, PO43-, Ni(CO)4, CH4 </li></ul>
  19. 24. Trigonal Pyramidal <ul><li>3 bonding pairs </li></ul><ul><li>1 lone pair </li></ul><ul><li>Bond angle of 107 </li></ul><ul><li>Examples; PH3, SO32-, NH3 </li></ul>
  20. 26. Bent/ Non-linear <ul><li>2 bonding pairs </li></ul><ul><li>2 lone pairs </li></ul><ul><li>Bond angle of 105 </li></ul><ul><li>Example; H2S, SO2, H2O </li></ul>
  21. 28. Trigonal Bipyramidal <ul><li>5 bonding pairs of electrons </li></ul><ul><li>0 lone pair </li></ul><ul><li>Bond angles of 120 and 90 </li></ul><ul><li>Example ; PCl5 </li></ul>
  22. 30. Octahedral <ul><li>6 bonding pairs </li></ul><ul><li>0 lone pair </li></ul><ul><li>Bond angle of 90 </li></ul><ul><li>Example; SF6 </li></ul>
  23. 33. Shapes and Bond Angles of Simple Organic Compounds
  24. 34. <ul><li>Organic Compounds- consisting of carbon and hydrogen mostly </li></ul>
  25. 41. Sp2 Hybridization