Question

can an electron lose all KE while in orbit around an nucleus

Answer 1

So long as it doesn't violate the uncertainty principal by doing so.

Answer 2

Speaking from physics point of view no it cannot.Because once it loses its energy means its velocity is zero so there is no centrifugal force which can balance the nucleus attraction making the electron unstable.

Answer 3

If absolute zero were possible (which it is not), in that event electrons orbiting nuclei would stop moving completely.

The closest anyone has come to cooling atoms (and therefore electrons) to absolute zero is when they were making Bose-Einstein Condensates (see wikipedia). At millionths of a degree above absolute zero, the electrons almost stop moving, but not quite.

So the answer to your question is that electrons cannot, so far as I am aware, loss ALL their kinetic energy.

Answer 4

As per my knowledge it should'nt..