Shapes of molecules 1) sketch the Lewis structure 2) locate the central atom 3) count regions of electron density around the central atom double/triple bonds and lone pairs count as ONE region of electron density 4) determine shape and angle bearing in mind that repulsion varies… lone pair-lone pair > lone pair-bonding pair > bonding pair-bonding pair

Linear 2 regions of electron density around the central atom, which is Beryllium 2 bonding pairs of electrons around the central atom there are no lone pairs of electrons around the central atom the regions of electron density are arranged as far as possible from each other, in order to maximise repulsion, making a LINEAR shape bond angle is 180 o eg’s H 2, HCl, CO 2, O 2, CS 2, N 2, HOCl, BeCl 2 ©

Trigonal planar 3 regions of electron density around the central atom, which is Boron 3 bonding pairs of electrons, around the central atom there are no lone pairs of electrons, around the central atom the regions of electron density are arranged as far as possible from each other, in order to maximise repulsion, making a TRIGONAL PLANAR shape With a bond angle is 120 o eg’s BCl 3, BCl 2 Br, BClBr 2, H 2 CO, COCl 2, SO 3 ©

Tetrahedral 4 regions of electron density around the central atom, which is carbon 4 bonding pairs of electrons around the central atom there are no lone pairs of electrons around the central atom the regions of electron density are arranged as far as possible from each other, in order to maximise repulsion, making a TETRAHEDRAL shape With a bond angle of 109 o eg’s SiH 4, CH 2 Br 2, SO 4 2-, PO 4 3-, SiCl 4, CF 4 ©

Trigonal pyramidal 4 regions of electron density around the central atom, which is Nitrogen 3 bonding pairs of electrons around the central atom there is one lone pair of electrons around the central atom the bond angle of 107 o (the lone pair of electrons takes up space as if they were a bond, so the arrangement is tetrahedral but because lone pairs repel more than bonding pairs, the bond angle is less than the expected angle of 109 o) TRIGONAL PYRAMIDAL shape eg’s NH 3, NF 3, PCl 3, AsH 3, AsF 3, PF 3 ©

V-shaped 4 regions of electron density around the central atom, which is Oxygen 2 bonding pairs of electrons around the central atom there are two lone pairs of electrons around the central atom the bond angle of 104 o (the two lone pairs of electrons take up space as if they were a bond, so the arrangement is tetrahedral but because lone pairs repel more than bonding pairs, the bond angle is less than the expected angle of 109 o) V-SHAPE or BENT eg’s H 2 O, OF 2, SCl 2 ©

Trigonal Bipyramidal 5 regions of electron density around the central atom, which is phosphorus 5 bonding pairs of electrons around the central atom there are no lone pairs of electrons around the central atom the regions of electron density are arranged as far as possible from each other, in order to maximise repulsion, making a TRIGONAL BIPYRAMIDAL shape Angles of 90 o and 120 o eg’s PCl 5, AsF 5 ©

Trigonal Bipyramidal - Seesaw 5 regions of electron density around the central atom, which is sulfur 4 bonding pairs of electrons around the central atom there is one lone pair of electrons around the central atom the one lone pair of electrons take up space as if they were a bond, so the arrangement is trigonal bipyramidal, specifically with a seesaw shape Angles of 90 o and 120 o TRIGONAL BIPYRAMIDAL – SEESAW shape eg’s SF 4, SCl 4 ClF 3 ©

Trigonal Bipyramidal – T-shaped 5 regions of electron density around the central atom, which is chlorine 3 bonding pairs of electrons around the central atom there are two lone pairs of electrons around the central atom the lone pairs of electrons take up space as if they were a bond, so the arrangement is trigonal bipyramidal, specifically t-shaped Angles of 90 o TRIGONAL BIPYRAMIDAL – T-SHAPED eg’s ClF 3, IF 3, BrF 3 ©

Trigonal Bipyramidal - Linear 5 regions of electron density around the central atom, which is iodine 2 bonding pairs of electrons around the central atom there are three lone pairs of electrons around the central atom the lone pairs of electrons take up space as if they were a bond, so the arrangement is trigonal bipyramidal, specifically linear Angles of 180 o TRIGONAL BIPYRAMIDAL – LINEAR eg’s [ICl 2 ] - ©

Octahedral 6 regions of electron density around the central atom, which is sulfur 6 bonding pairs of electrons around the central atom there are no lone pairs of electrons around the central atom the regions of electron density are arranged as far as possible from each other, in order to maximise repulsion, making an Octahedral shape all bond angles are 90 o OCTAHEDRAL shape eg’s SF 6, PF 6 -, PCl 6 - ©

Octahedral - Square pyramid 6 regions of electron density around the central atom, which is bromine 5 bonding pairs of electrons around the central atom there is one lone pair of electrons around the central atom the lone pairs of electrons take up space as if they were a bond, so the arrangement is octahedral, specifically square pyramid Angles of 90 o OCTAHEDRAL – SQUARE PYRAMID eg’s BrF 5, IF 5 ©

Octahedral - Square planar 6 regions of electron density around the central atom, which is xenon 4 bonding pairs of electrons around the central atom there are two lone pairs of electrons around the central atom the lone pairs of electrons take up space as if they were a bond, so the arrangement is octahedral, specifically square planar Angles of 90 o OCTAHEDRAL – SQUARE PLANAR eg BrF 4 -, ICl 4 - ©