Shape Of Covalent Molecules +1

Shapes of Molecules

Key Concepts A molecule consists of 2 or more atoms joined by covalent bonds. The shape of a molecule is a description of the way the atoms in the molecule occupy space. A diatomic molecule, a molecule composed of only 2 atoms, must always be linear in shape as the centers of the 2 atoms will always be in a straight line. 'Electron Cloud' Repulsion Theory (Valence Shell Electron Pair Repulsion, VSEPR) is used to predict shapes and bond angles of simple molecules an 'electron cloud' may be a single, double or triple bond, or a lone pair of electrons a lone pair of electrons is a non-bonding pair of electrons 'electron clouds' are negatively charged since the electrons are negatively charged, so electron clouds repel one another and try to get as far away from each other as possible lone pairs of electrons exert a greater repelling effect than bonding pairs do lone pair-bonding pair repulsion is greater than bonding pair-bonding pair repulsion lone pair-lone pair repulsion > lone pair-bonding pair repulsion > bonding pair-bonding pair repulsion Total Number of electron pairs Arrangement of electron pairs Number of bonding pairs of electrons Number of lone pairs of electrons Shape of Molecule Name of Shape Bond Angle Examples not applicable linear 1 not applicable linear 180o H2, HCl 2 linear 2 0 linear 180o CO2, HCN 3 trigonal planar 3 0 triganol planar 120o BCl3, AlCl3 4 tetrahedral 4 0 tetrahedral 109.5o CH4, SiF4 3 1 trigonal pyramidal <109.5o(bond angles in ammonia, NH3, are 107o) NH3, PCl3 2 2 bent <109.5o(bond angles in water, H2O, are 105o) H2O, SCl2 5 trigonal bipyramidal 5 0 trigonal bipyramidal 120o in the trigonal planar part of the molecule, 90o for the others PCl5 6 octahedral 6 0 octahedral 90o SF6 For More InFo Visit    http://www.ausetute.com.au/shapemol.html