Why is potential energy of atoms zero at infinity?
Answers
Explanation:
The potential energy of interaction between a nucleus (at the origin) and an electron as a function of the distance r between them. The potential energy is zero when the two particles are very far apart (r = ¥ ), and equals minus infinity when r equals zero.
Answer: It is not exactly 'zero' at infinity or anything. Infact, we don't talk about potential energy of a particle like 'atom' or 'electron' at all! Don't get me wrong - potential energy refers to the energy acquired by a particle due to virtue of its configuration(position). Say, you have an ion(I'll talk about an atom which has gained or lost an electron for now) at a tremendous distance from a charge you're holding. Let's assume the charge you're holding and the ion are the only two objects in the universe. An electrostatic force of attraction/repulsion acts between the ion and the charge. The charge on the two particles, along with their seperation(configuration) constitute the potential energy of both the particles(as I mentioned, potential energy of a single particle is meaningless; there either has to be a conservative force field or another interacting particle producing a field). Now, potential energy(in the electrostatic case for point charges) varies inversely as the square of the distance, i.e., at large separations, the value of potential energy tends to become very small. Theoretically, if we extrapolate this behaviour to an 'infinite' separation, the potential energy will, theoretically, vanish.
Further, you're not bound to assume that it is zero at infinity. You can choose it to be zero at any point you wish. Potential energy is not a physically meaningful quantity; what is actually meaningful is the potential energy difference.