In the early nineteenth century it was also established
that each element is associated with a characteristic
spectrum of radiation, for example, hydrogen always gives
a set of lines with fixed relative position between the lines This fact suggested an intimate relationship between the
internal structure of an atom and the spectrum of
radiation emitted by it In 1885, Johann Jakob Balmer
(1825 – 1898) obtained a simple empirical formula which
gave the wavelengths of a group of lines emitted by atomic
hydrogen Since hydrogen is simplest of the elements
known, we shall consider its spectrum in detail in this
chapter