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