Difference between emission spectrum and absorption spectrum

What are emission and absorption spectra?

Emission and absorption spectra are graphical representations of the radiant energy emitted or absorbed by a chemical substance. Both types of spectra are used to identify the physical and chemical properties of elements and compounds.

Emission spectra

Emission spectra are generated by the emission of energy from a substance when excited by an external source, such as a flame or electric arc. Electrons in the substance jump to higher orbitals and release energy in the form of light. Each chemical element has a pattern of unique emission lines that can be used to identify the presence of that element in a sample.

Example of emission spectrum

In this example, the emission spectrum of hydrogen is shown. Each line in the spectrum represents a unique transition of an electron from one orbit to another. These transitions release energy in the form of light, and each line corresponds to a specific wavelength.

Absorption spectra

Absorption spectra are generated by the absorption of radiant energy by a substance. These spectra are useful for identifying unknown substances, since each element and compound absorbs radiant energy at a particular wavelength. An absorption spectrum shows the points on an emission spectrum where absorptions have occurred.

Example of absorption spectrum

In this example, the absorption spectrum of a molten salt is shown. The dark line on the spectrum indicates that the salt has absorbed radiant energy at that particular wavelength.

Conclusions

Both emission and absorption spectra are valuable tools in the identification of elements and compounds. Emission spectra are produced by the emission of radiant energy, while absorption spectra are generated by the absorption of radiant energy. Both types of spectra have unique patterns for each element and compound, making it easier to identify unknown substances.

• Emission spectra: Graphic representation of the radiant energy emitted by a substance when excited by an external source, such as a flame or electric arc.
• Absorption spectra: Graphic representation of the radiant energy that a substance absorbs.
• Identification of elements and compounds: Emission and absorption spectra have unique patterns for each element and compound, making it easier to identify unknown substances.