# What happens to the electronic movements at absolute 0?

what happens to the motion of electrons in the their respective orbits when a substance is cooled down to zero kelvin? assuming they stop moving then are they gonna stick to the nucleus? if yes what happens when it's brought back to ordinary temperature, will it still be stuck? what about the entropy in the whole process?

• Electrons don't have classical orbits. Classical trajectories don't make sense when the effects of Heisenberg's uncertainty principle are significant. – PM 2Ring May 5 at 22:03

In a world described by Classical Physics, temperature would always be proportional to kinetic energy. Therefore, $$T=0$$ would correspond to a state with no kinetic energy, which in turn would imply all velocities equal to zero , i.e. no movement.
QM breaks the argument for no movement at $$T=0$$ in correspondence of two conceptual points:
2. The classical relation between kinetic energy and temperature (equipartition theorem) breaks for quantum systems. It is still possible to introduce the thermodynamic definition of temperature ( $$T=\frac{\partial{U}}{\partial{S}}$$ ) but in this case $$T=0$$ does not imply zero kinetic energy.