I KNOW i am overgen................i am doing it on purpose.......to show the process involved......


This discussion of the property of spin leads us to one of the most important principles in quantum physics, the Pauli exclusion principle (formulated by Wolfgang Pauli in 1925), which states that no two identical fermions may occupy the same quantum state simultaneously (although two electrons, for example, may acquire opposite spin in order to differentiate their quantum states). Another way of stating the principle is that no two fermions in a quantum system can have the same values of all four quantum numbers at any given time. This principle effectively explains the continued existence of very high density white dwarf stars, but also the very existence of different types of atoms in the universe and the large-scale stability and bulk of matter.

(Click for a larger version) Electron shell diagram for the element uranium (using the Bohr model of the atom) (Source: Wikipedia: http://en.wikipedia.org/wiki/Wikipedia: Picture_peer_review/Electron_shells)

To understand why, it is necessary to know that, according to the Bohr model of the atom, electrons in an atom (which exist in the same quantity as the number of protons in the nucleus of the particular atom, so that the overall electric charge is zero) are constrained to occupy certain discrete orbital positions or “shells” around the nucleus. The closer electrons are to the nucleus, the more strongly the electric force is pulling them in and the more energy would be required to free it from the clutches of the nucleus (or, looked at another way, the more energy of its own an electron has, the less additional energy it needs in order to escape). The innermost shell can accommodate just two electrons, one with spin “up” and one with spin “down” in order to differentiate their quantum states. The next shell out, in a higher energy level, can accommodate a further eight, the next a further eighteen and the next thirty-two.