For under certain conditions the chemical atoms emit light waves of a specific length or oscillation frequency - their familiar characteristic spectra - and these can come in the form of electromagnetic waves only from accelerated electric quanta.

If the experimental physicist has already done a great deal of work in this field, nevertheless the theoretical physicist has still hardly begun to evaluate the experimental material which may lead him to conclusions about the structure of the atom.

Moreover, the abundance of chemical compounds and their importance in daily life hindered the chemist from investigating the question, in what does the individuality of the atoms of different elements consist.

It is more likely that more than a century will pass before we know the structure of the chemical atoms as thoroughly as we do our solar system.

The removal of an electron from the surface of an atom - that is, the ionization of the atom - means a fundamental structural change in its surface layer.

We have learnt through experience that when an electrical ray strikes the surface of an atom, an electron, and in some circumstances a second and even a third electron, can be detached.

The movement of the emitters of the spectral lines may be deduced on the basis of the Doppler principle.