I asked the following question to my science teacher:

If the lowest temperature, theoretically, is when the motion of electrons around the nucleus ceases, then what happens when they are orbiting at the speed of light, meaning, according to traditional physics, the fastest they could get, and thus the hottest temperature. Does the atom split or something?

He told me that the temperature of an atom or molecule is not determined by electronic motion. I still disagree - because the motion of the atom or molecule as a whole does not make sense in causing the temperature of a substance. So can anyone answer the question of what exactly causes temperature. I'd also like to find an answer to the question I asked my science teacher.