Do electrons always stay in the same orbital?

Answer 1

Never

Electrons do not revolve around the atomic nucleus. Classical physics breaks down at this level, and even if it didnt, we would not be able to observe such behavior, as any device used for observing would have to use electromagnetic radiation (light, xrays, etc), which would alter the position and/or velocity of the electron, per the uncertainty principle. The math is very complex, and beyond me, but an electrons position around a nucleus can be described as a standing wave, with degrees of probability assigned to each point around the nucleus. the different electrons each tend to occur in a probability region that allows them to sort of fit together with each other, like a jigsaw. interestingly, the probability field extends to infinity, such that in theory an electron associated with an atom in my body may exist in your body, or anywhere in the universe, at any given moment. This, however, is very rare, with an electron existing closer to another atom than its associate one probably only a few times in all of the history of the universe. (i dont have the numbers in front of me, so i could be way off, but you get the idea)

Answer 2

No, electrons can be promoted to a higher level orbital by absorbing electromagnetic radiation of the proper frequency. They then reemit this energy and drop back down to their "ground state". This is responsible for the phenomena of fluorescence and phosphorescence, and the glow of a neon light.

Answer 3

No. Chemical changes or ionization can change the number of electrons, and atoms of solid and liquid metals share electrons.