What is the outcome when an electron falls to a lower energy shell?

When an electron falls to a lower energy shell, the outcome is that a photon can be released. This process occurs because electrons occupy discrete energy levels in an atom, known as shells. When an electron transitions from a higher energy level to a lower one, the energy difference between these two levels is released in the form of a photon.

The energy of the emitted photon corresponds exactly to the energy difference between the two shells, adhering to the principle of conservation of energy. This is a crucial concept in quantum mechanics and is responsible for phenomena such as the emission spectra of elements, where specific wavelengths of light are emitted based on the transitions of electrons between energy levels.

In contrast, the other options do not accurately describe the outcome of an electron falling to a lower energy shell. For instance, an electron transition to a lower energy level does not involve absorption of a photon or the loss of energy as heat in this context, nor does it lead to the disintegration of the atom. The atom remains intact, and this process instead contributes to its electromagnetic properties.