van der Waals forces

Relatively weak electrical forces that attract neutral (uncharged) molecules to each other in gases, liquefied and solidified gases, and almost all organic liquids and solids. Solids held together by van der Waals forces typically have lower melting points and are softer than those held together by ionic, covalent, or metallic bonds (see bonding). The forces arise because neutral molecules, though uncharged, are usually electric dipoles, which have a tendency to align with each other and to induce further polarization in neighbouring molecules, resulting in a net attractive force. They are somewhat weaker than the forces involved in hydrogen bonding. See also Johannes D. van der Waals.