dISPERSION FORCES |
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The London dispersion force is the weakest intermolecular force. The London dispersion force is a temporary attractive force that results when the electrons in two adjacent atoms occupy positions that make the atoms form temporary dipoles. Because of the constant motion of the electrons, an atom or molecule can develop a temporary (instantaneous) dipole when its electrons are distributed unsymmetrically about the nucleus. |
London dispersion forces affect boiling point. For example, larger atoms have stronger London dispersion forces affecting them, thus holding them together stronger, increasing the energy required to pull them apart and thus the boiling temperature. For example the halogens (from smallest to largest: F2, Cl2, Br2, I2). Fluorine and chlorine are gases at room temperature, bromine is a liquid, and iodine is a solid. |