When a photon is emitted by an atom, what happens to the energy state of the atom?

When a photon is emitted by an atom, the atom transitions from a higher energy state to a lower energy state. This process involves the release of energy in the form of the emitted photon, which corresponds to the difference in energy between the two states.

In this context, the emission of a photon indicates that the electron within the atom has moved to a lower energy orbital, resulting in a decrease in the overall energy level of the atom. This principle is a fundamental aspect of quantum mechanics, where energy levels are quantized, and photons represent quantized packets of energy. The energy of the emitted photon can be calculated using the equation E = hν, where E is the energy of the photon, h is Planck's constant, and ν is the frequency of the emitted photon.

Thus, the correct choice reflects the decrease in energy level that occurs when an atom emits a photon.