What force is responsible to keep electrons in motion?

Question

Are electrons in an atom are in motion? If yes, then what force is responsible to keep electrons in motion in an atom?

Answer 1

So roughly speaking this is the contents of Newton's first law.

Newton was living in an era when people wanted to think that the natural state was things standing still, and that all motion required a force to explain it. But but during Newton's life, Galileo had observed something different: when he rolled a smooth metal ball over a large flat floor, it had no intrinsic tendency to stop; it just wanted to keep going in a straight line. Newton elevated this idea to the status of a law of motion, saying that uniform motion in a straight line was the natural state, and deviations from that motion needed forces to explain them. So the fact that things slow down and eventually come to.rest, requires now an explanation (namely friction).

Indeed, to lose or gain energy now generally requires an explanation of where that energy went, until you get to galactic-scale systems and general relativity, where you cannot extend certain “local” definitions to apply “globally” any more. So the electron does not need, in this worldview, a special force to keep it moving: it just has to be prevented from losing the energy of motion that it has, to other systems. And that is the statement of quantum mechanics: this thing can only occupy certain discrete energy levels and there is no lower-energy “stopped” state available for the electron to fall into. The lowest state is not stopped because the electron has an intrinsic spin and when it occupies the non-rotating probability cloud spherically symmetric around the nucleus, that spin at each point looks like a rotation of the whole cloud. The higher states for e.g. Lithium, that one electron is not able to fall into the lower less-rotating energy states because they are already occupied by other electrons, so it must take one of the spinny energy states that has intrinsic orbital angular momentum.

Answer 2

"Forces" don't keep things in motion - that was the old idea of Aristotelian mechanics, and it is not a good principle for understanding the rest of the Universe, already dated by the time of Sir Isaac Newton. "Forces" influence motion, but "motion" exists of its own accord.

So what I suppose you are really asking is "what force confines the electrons to stay near the atomic nucleus" - that is, which force influences them to stay near the nucleus and not, say, wander off into space. The answer to that is electromagnetism.

The nucleus has a positive electric charge. The electrons have a negative charge. Positive charges exert attractive forces on negative charges, and conversely. This pulls them together.

The electrons gets as close as they can to the nucleus. The size of the atom is set, intuitively, by the point at which the amount of information that would be required to more precisely define the electron's location (by being in a smaller area, you need a more precise number, in a sense, to tell where it is) together with that to define its motion (so as to say it's confined), combined, is at or around the maximum limit the Universe allots to any particle.