The classical theory of electromagnetic interactions. It is not possible to understand the structure of atoms in terms of classical electrodynamics. In the case of electrostatics, i.e. the interaction of electrically charged particles, Earnshaw’s theorem prevents the existence of stable atoms. In the Rutherford model, classical electrodynamics shows that an electron should very rapidly spiral into the nucleus, emitting electromagnetic radiation while doing so. The interaction between electromagnetic radiation and atoms and molecules can frequently be treated by analysing the atom or molecule using quantum mechanics, and the electromagnetic radiation using classical electrodynamics.