Shape of Molecule
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1) The shape of a molecule can be predicted using the electron pair repulsion theory, which states that molecules form shapes that minimize repulsive forces between bonding pairs. 2) Regular molecular shapes are determined by counting the number of bonding pairs - two pairs is linear, three is trigonal planar, four is tetrahedral, etc. 3) Irregular shapes can occur when lone pairs are present, causing distortions from the regular geometries.
Shape of Molecule
- 1. SHAPES OFSHAPES OF MOLECULESMOLECULES COVALENTBONDCOVALENTBOND ByBy RIMKHONG GROUPRIMKHONG GROUP
- 2. LOOK AT THIS VDOLOOK AT THIS VDO
- 3. Before you start it would be helpful to… • know the definition of a covalent bond • know what a lone pairis • know that like charges repel SHAPES OF MOLECULESSHAPES OF MOLECULES
- 4. is the chemical bond that involves the sharing of pairs of electrons between atoms. Covalent BondCovalent Bond
- 5. ELECTRON PAIR REPULSION THEORYELECTRON PAIR REPULSION THEORY “THE SHAPE ADOPTED BY A SIMPLE MOLECULE OR ION IS THAT WHICH KEEPS REPULSIVE FORCES TO A MINIMUM” Al Bonds are further apart so repulsive forces are less Bonds are closer together so repulsive forces are greater Al All bonds are equally spaced out as far apart as possible
- 6. REGULAR SHAPESREGULAR SHAPES Molecules, or ions, possessing ONLY BOND PAIRS of electrons fit into a set of standard shapes. All the bond pair-bond pair repulsions are equal. All you need to do is to count up the number of bond pairs and chose one of the following C A covalent bond will repel another covalent bond examples...
- 7. REGULAR SHAPESREGULAR SHAPES 2 LINEAR 180º BeCl2 3 TRIGONAL PLANAR 120º AlCl3 4 TETRAHEDRAL 109.5º CH4 5 TRIGONAL BIPYRAMIDAL 90º & 120º PCl5 6 OCTAHEDRAL 90º SF6 BOND BOND PAIRS SHAPE ANGLE(S) EXAMPLE
- 8. BERYLLIUM CHLORIDEBERYLLIUM CHLORIDE Cl ClBe 180° BOND PAIRS 2 LONE PAIRS 0 BOND ANGLE... SHAPE... 180° LINEAR ClBe Be ClCl LINEAR LINEAR
- 9. Al ALUMINIUM CHLORIDEALUMINIUM CHLORIDE Cl Cl Al 120° Cl Cl Al Cl Cl Cl BOND PAIRS 3 LONE PAIRS 0 BOND ANGLE... SHAPE... 120° TRIGONAL PLANAR RIGONAL PLANAR
- 10. METHANEMETHANE BOND PAIRS 4 LONE PAIRS 0 BOND ANGLE... SHAPE... 109.5° TETRAHEDRAL C H CH H H H 109.5° H H C H H ETRAHEDRAL
- 11. PHOSPHORUS(V)FLUORIDEPHOSPHORUS(V)FLUORIDE FP P F F F F F BOND PAIRS 5 LONE PAIRS 0 BOND ANGLE... SHAPE... 120° & 90° TRIGONAL BIPYRAMIDAL 120° F F P F F F 90° TRIGONAL BIPYRAMIDAL TRIGONAL BIPYRAMIDAL
- 12. SULPHUR(VI) FLUORIDESULPHUR(VI) FLUORIDE FS BOND PAIRS 6 LONE PAIRS 0 BOND ANGLE... SHAPE... 90° OCTAHEDRAL S F F F F F F F F F F S F F 90° CTAHEDRAL CTAHEDRAL
- 13. ARE YOU OK! summary To predict the shape of a molecule: (1)Write down the Lewis dot structure for the molecule. (2)Count the number of bond pairs and lone pairs around the central atom. (3) Decide on the electron pair orientation based on the total number of electron pairs (4 = tetrahedral, 5 = trigonal bipyramidal). (4) Consider the placement of lone pairs and any distortions from "regular" shapes. (5) Name the shape based on the location of atoms
- 14. summary
- 15. CO2 CCl4 NCl5 HCN BCl3 NH3 TEST QUESTIONS For each of the following molecules state the number of bond pairs state the shape state the bond angle(s)
- 16. CO2 CCl4 NCl5 HCN BCl3 NH3 Linear BOND BOND PAIRS SHAPE ANGLE(S) 2 180º Tetrahedral4 109.5º Trigonal BipyramidalTrigonal Bipyramidal55 90º 120º90º 120º Linear2 180º Trigonal PlanarTrigonal Planar33 120º120º Trigonal PyramidalTrigonal Pyramidal33 107º107º TEST QUESTIONS
- 17. SHAPES OFSHAPES OF MOLECULESMOLECULES The EndThe End