Intermolecular forces

• A hydrogen bond is a bridge structure between a hydrogen atom bonded to an electronegative atom, and a lone pair of electrons in another molecule
• A permanent dipole-dipole is the force of attraction between oppositely charged dipoles
• The number of lone pairs determines how many hydrogen bonds a molecule can form
• Van de Waals forces arise when electron movement in one molecule creates a temporary dipole and induces a dipole in another molecule, so a temporary attraction between molecules arise
• Permanent dipole-dipole interactions are formed due to a difference in electronegativity between the atoms causing bond polarity, so an attraction between opposite partial charges
• Hydrogen bonds are constantly formed and broken as water molecules are free to move around, meaning density is higher
• Water molecules are held at fixed distances apart in a tetrahedral lattice, so there is a lot of space between molecules, giving ice an open structure and a lower density than liquid water
• The more lone pairs a molecule has, the more hydrogen bonds it can form, so the higher its boiling point is