When an electron transitions from an excited state to its ground state in an atom, it releases energy in the form of electromagnetic radiation. This process is known as emission.
During the excited state, the electron occupies an energy level that is higher than the ground state. This higher energy level is typically achieved when the electron absorbs energy, such as through the absorption of photons or collisions with other particles. The electron exists in this excited state temporarily and then transitions back to the ground state.
As the electron returns to the ground state, it loses energy. This lost energy is released in the form of a photon, which carries away the excess energy. The energy of the emitted photon corresponds to the energy difference between the excited state and the ground state. This energy is typically released as visible light, but it can also be released as ultraviolet, infrared, or other forms of electromagnetic radiation depending on the specific transition.
The reason for this energy release and the transition to the ground state lies in the quantum mechanical nature of electrons in atoms. Electrons can only occupy certain discrete energy levels in an atom. When an electron absorbs energy, it transitions to a higher energy level. However, this higher energy state is not stable, and the electron tends to return to its lowest energy state, which is the ground state. This transition releases the excess energy as a photon.
In summary, when an electron transitions from an excited state to the ground state, it loses energy. This lost energy is emitted as a photon, resulting in the emission of electromagnetic radiation. This process occurs due to the quantum mechanical nature of electrons and their tendency to occupy the lowest energy states available in an atom.