The significant break through in chemistry was made during last two centuries wherein we analysed the subject more minutely, even upto the level of the smallest creative and functional unit of substances i.e. atom, which is involved in all sorts of chemistry any how.
During this span of time atoms could be fragmented into still finer subatomic constituents and existence of nucleus was confirmed. Some of the legendry chemists could manage to peep inside the atom and gave every detail about the atomic world through their atomic models. Bohr gave the detail profile of orbiting electrons and successfully explained the line spectrum of hydrogen. With the unfolding of the structure of atom the chemical science passed from its infancy state i.e. crude, empirical and macroscopic state to scientific, rational, microscopic and mature state of understanding.
Infact, the outlook of every chemistry of a substance is a reflection of ingoing business of extra nuclear electrons. So the idea regarding arrangement of electrons around the nucleus is essential to understand the chemical behaviour on atomic level. This topic will be concluded with the explicit detail about electronic configuration to make the fascinating chemistry lucid and comprehensive.