# Total energy of an electron

The KE (kinetic energy) of an electron revolving around a nucleus is always positive, and the PE (potential energy) of an electron is negative (except at infinity, where it is zero). Here, I am speaking from the point of view of the Rutherford model. The material from which I am reading from says that the electron will not follow a closed orbit around the nucleus if the TE is positive. Also, I am aware of the fact that the magnitude of PE is twice of that of KE. So it is not surprising why the TE is is negative. But, I do not get the physical significance of negative energy. Can someone please tell me where I am going wrong...Thank you

## Answers and Replies

jtbell
Mentor
I do not get the physical significance of negative energy.

It means that you have to do positive work on the system (electron + nucleus) to separate it, that is, bring its total energy up to zero. We define the zero-point of energy in this situation to be when the electron and nucleus are "just barely unbound" from each other, infinitely far from each other and at rest.

It means that you have to do positive work on the system (electron + nucleus) to separate it, that is, bring its total energy up to zero. We define the zero-point of energy in this situation to be when the electron and nucleus are "just barely unbound" from each other, infinitely far from each other and at rest.

OH! I get it now. Thanks a ton