Atoms and Electromagnetic Spectra

Key Questions

  • Electromagnetic (EM) radiation is a stream of photons, traveling in waves. The photon is the base particle for all forms of EM radiation

    But what's a photon? It's a bundle of energy -- of light -- always in motion. In fact, the amount of energy a photon carries makes it sometimes behave like a wave and sometimes like a particle.

    Scientists call this wave-particle duality. Low-energy photons (such as radio) behave like waves, while high-energy photons (such as X-rays) behave more like particles.

    EM radiation can travel through empty space. This differentiates it from other types of waves, such as sound, which need a medium to move through.

    All forms of EM radiation reside on the electromagnetic spectrum, which ranks radiation from lowest energy/longest wavelength to highest energy/shortest wavelength.
    The higher the energy, the stronger, and therefore more dangerous, the radiation.


  • Answer:

    Each element has its own unique atomic emission spectrum. You can look at the spectra and identify which elements are present.


    When an atom absorbs energy, its electrons jump to higher energy levels. Then they jump back down again. Each jump corresponds to a particular wavelength of light.

    There are many possible electron transitions for each atom. Each transition has a specific energy difference. This collection of transitions makes up an emission spectrum. These emission spectra are as distinctive to each element as fingerprints are to people.

    Thus, scientists can use atomic spectra to identify the elements in them. You can view the atomic spectrum of each element at

    Here is a look at emission (colors of light) produced by four different elements.

    Video from: Noel Pauller

    This video show uses diffraction grating to show the emission spectra of several elements including hydrogen, oxygen, neon and nitrogen.

    Video from: Noel Pauller

    Use of a tool such as a spectroscope would allow someone to determine the different wavelengths each of these elements is giving off. The color you observe in the video is the sum total of all of the visible emissions from each element.

    A common lab performed in chemistry involves flame tests of different metal salt compounds. Different compounds will give off different colors of light. The color can be used to identify which elements are present in the salt.

    Hope this helps!