Molecular shapes can be predicted by the: Valence Shell Electron Pair Repulsion (VSEPR) theory. There are 5 ideal molecular shapes in this theory. A is always the central atom and X represents the terminal atoms in the molecule. Using the above symbols, the 5 shapes are represented by: VSEPR models AX2, AX3, AX4, AX5, AX6. 1 Linear shapes (in a straight line) have 1800 between the bonds. General formula: AX2 Bond angle: 1800 Examples: CO2 & BeCl2 Linear CO2 molecule 2 Here the bond angles are 1200 to each other – in the same plane: General formula: AX3 Bond angle: 1200 Examples: BF3 & BCl3 BF3 trigonal planar molecule 3 Here the 4 terminal atoms are positioned in the tetrahedron formation with bond angles at 109,50 to each other: Tetrahedral shape Name: Tetrahedral shape General formula: AX4 Bond angle: 109,50 Examples: CH4 & CCl4 There are other variations of this shape: consider H2O & NH3. Lone pairs of ē repel bonding pairs. 4 Here the 5 terminal atoms are connected in a trigonal, bypyramidal structure General formula: AX5 Bond angle: 1200 & 900 Example: PCl5 Trigonal bipyramidal shapes 5 Here the 6 terminal atoms bond with the central atom to form an octahedral shape General formula: AX6 Bond angle: 900 Example: SF6 Octahedral shapes 6 ∂ -- O O=C=O H linear molecule with polar bonds 1800 ∂+ H Polar angular molecule with polar bonds 104,50 VSEPR summary H ∂- - H N C H ∂+ H H H Polar pyramidal shape with polar bonds 107.30 H N ...
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