12&13Shapes of Molecules & Intermolecular Forces - B.pdf

Shapes of Molecules & Intermolecular Forces 1. Linear: Can have 2 or 3 atoms 2. V-Shaped: 3 atoms 3. Trigonal Planar: 4 atoms 4. Pyramidal: 4 atoms 5. Tetrahedral: 5 atoms  Electron Pair Repulsion Theory - Electron pairs can be either: 1. Bond pairs 2. Lone pairs  These electron pairs arrange them...

Shapes of Molecules & Intermolecular Forces 1. Linear: Can have 2 or 3 atoms 2. V-Shaped: 3 atoms 3. Trigonal Planar: 4 atoms 4. Pyramidal: 4 atoms 5. Tetrahedral: 5 atoms  Electron Pair Repulsion Theory - Electron pairs can be either: 1. Bond pairs 2. Lone pairs  These electron pairs arrange themselves around a central atom. As they do, they repel each other & end up as far apart as geometrically possible  The order of strength of repulsion is: lp : lp > lp : bp > bp : bp  some molecules can have polar bonds, but be non-polar overall. This occurs when a molecule has a high degree of symmetry, and also has a geometric centre  Dipoles are separated centres of charge.  Intra means within.  Inter means between.  Intermolecular forces – a ects Boiling point  Types of Intramolecular forces Van der Waals forces - Van der Waals forces are weak attractive forces between molecules resulting from the formation of temporary dipoles. Dipole – dipole interactions - These occur between polar molecules where permanent dipoles exist. Stronger than VDW Hydrogen bonding - Hydrogen bonding is a special type of dipole – dipole interaction, which occurs when hydrogen is bonded to small, highly electronegative elements such as O, N, or F Intramolecular 1)Van Der Waals (weak) 2)Dipole-dipole (medium) 3)Hydrogen bonds (strong) Intermolecular 1)non-polar covalent 2)polar covalent