How do excited atoms emit radiation

These emit ultraviolet light when the excited electrons return to lower energy levels. A substance coated on the inside of the glass absorbs the ultraviolet light and emits visible light. Atoms are electrically neutral because:. However, an outer electron may absorb enough electromagnetic radiation to leave the atom entirely. When this happens, the atom becomes a positively charged ion. The process is called 'ionisation' - the atom has been ionised.

Molecules can be ionised if one or more of their atoms become ionised. Radiation that can ionise atoms and molecules is called ionising radiation. Alpha, beta and gamma radiations are examples of ionising radiation. Radiation interacting with matter The nucleus of an atom is surrounded by electrons.

Visible light displays classical wave-like properties, but it also exhibits properties reminiscent of particles, which are manifested through entities that possess energy and momentum but no mass , and are referred to as photons. The atom is the source of all forms of electromagnetic radiation, whether visible or invisible. Higher-energy forms of radiation, such as gamma waves and X-rays, are produced by events that occur to disrupt the nuclear stability of the atom.

Radiation having lower energy, such as ultraviolet, visible, and infrared light, as well as radio and microwaves, originate from the electron clouds that surround the nucleus or the interaction of one atom with another. These forms of radiation occur due to fact that electrons moving in orbits around the nucleus of an atom are arranged in different energy levels within their probability distribution functions.

Many of the electrons can absorb additional energy from external sources of electromagnetic radiation see Figure 3 , which results in their promotion to an inherently unstable higher energy level.

Eventually, the "excited" electron loses the extra energy by emitting electromagnetic radiation of lower energy and, in doing so, falls back into its original and stable energy level.

The energy of the emitted radiation equals the energy that was originally absorbed by the electron minus other small quantities of energy lost through a number of secondary processes. Electromagnetic radiation energy levels can vary to a significant degree depending upon the energy of source electrons or nuclei.

Likewise, when the atoms relaxed back to a lower energy state, any amount of energy could be released. This would result in what is known as a continuous spectrum , where all wavelengths and frequencies are represented.

White light viewed through a prism and a rainbow are examples of continuous spectra. Atomic emission spectra were more proof of the quantized nature of light and led to a new model of the atom based on quantum theory. Atomic Emission Spectra The electrons in an atom tend to be arranged in such a way that the energy of the atom is as low as possible. Electrons in the gaseous atoms first become excited, and then fall back to lower energy levels, emitting light of a distinctive color in the process.

Shown are gas discharge tubes of helium, neon, argon, krypton, and xenon. Each of these spectral lines corresponds to a different electron transition from a higher energy state to a lower energy state. Summary Atomic emission spectra are produced when excited electrons return to the ground state. The emitted light of electrons corresponds to energies of the specific electrons.