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Significance of Negative sign in energy expression. |
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Answer» The negative sign in the energy expression appears because the energy of a free electron at rest is taken as zero. Such an electron would be at infinite distance away from the nucleus and would not experience any force of attraction towards it. As it comes closer, it experiences stronger and stronger attractive force and its energy would decrease. Since it is less than zero, it would have negative sign. The energy of the electron would be lowest in the orbit with n = 1 and this most stable state is known as the ground level. If the electron has to jump to the next orbit with n = 2, some energy must be given to it to overcome the attractive force of the nucleus. Thus in the second orbit, the energy of the electron is greater than is the first. Similarly, as the electron shifts from the second to the third, fourth and so as, its energy would increase. |
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