Just as Bohr.s model of atom was developed on the basis of planck.s quantum theory, wave mechanical model of atom has been developed on the basis of quantum mechanics. The herat of quantum mechanism is Schrodinger wave equation which in turn is based on Heisenberg.s uncetainity principle and de broglie concept of dual nature ofmatter and radiation. Bohr model could explain the main lines of hydrogen or hydrogenic spectra but could not explain their fine structure. To explain this, it was suggested that each level consists of a number of sublevels, it was suggested that each level consists of a number of sublevels, the transitions between which gave rise to closely spaced lines. The numbers representing the main energy level are called Princiapl Quantum Number (n) while those representing sublevels are called Azimuthal Quantum numbers (l) and these determine the angular momentum of the electron. The orbital angular Number (m) which is just like a further split of a sublevel into finer sublevels. Lastly the electron may rotate or spin about its own axis given rise to Spin Quantum number (s) which determines the angular momentum of the electron. The electron spin magnetic moment of Fe^(2+) ion in FeSO_(4) in Bohr magnetons (B.M) is