What are energy levels, and how do they relate to the Bohr model?
Energy levels are discrete states of energy that electrons can occupy in an atom. In the Bohr model, these levels are defined by the electron's distance from the nucleus. The closer an electron is to the nucleus, the lower its energy. When an electron absorbs energy, it can move to a higher energy level (excited state), and when it loses energy, it returns to a lower level (ground state), often emitting a photon in the process.