Emission spectra color characteristics

Each element s atomic emission spectrum is unique and can be used to determine if that element is part of an unknown compound. For example, when a platinum wire is dipped into a strontium nitrate solution and then inserted into a burner flame, the strontium atoms emit a characteristic red color. You can perform a series of flame tests yourself by doing the miniLAB below. 

Electrons star again as color hlazes up when atoms are heated in a Bunsen flame. The characteristic color produced hy an element in a flame test is sometimes used to identify that element. More information can be obtained if the colored light from the flame is put through a spectrophotometer that can separate it into the individual lines of an emission spectrum. You learned about the emission spectra of atoms in Chapter 2, and how spectra provide evidence about electrons in atoms. 

Each element has a characteristic line spectrum that can be used to identify the element. Note that line emission spectra can also be obtained by heating a salt of a metal with a flame. For instance, common salt (sodium chloride) provides a strong yellow light to the flame coming from excited sodium, while copper salts emit a blue-green light and lithium salts a red light. The colors of fireworks are due to this phenomenon. 

The luminescence of the lanthanide ions spreads from the UV spectral range up to the NIR, and many lanthanide ions have unique spectral characteristics in the visible region of the spectrum, which also give them distinctive luminescent colors. A lot of applications take advantage of those characteristic emissions for color reproduction and lighting. Phosphors, nanomaterials made of lanthanide complexes or enclosing lanthanide compounds, as well as LEDs based on lanthanide complexes are extensively investigated. 

An emission spectrum is produced when atoms in an excited state emit photons characteristic of the eiement as they return to iower energy states. The characteristic colors of fireworks and sodium-vapor streetlights are due to one or a few prominent lines in the emission spectra of the atoms present. 

Each element, in fact, has a characteristic line spectrum because of the emission of light from atoms in the hot gas. The spectra can be used to identify elements. How is it that each atom emits particular colors of light What does a line spectrum tell us about the structure of an atom If you know something about the structures of atoms, can you explain the formation of ions and molecules We will answer these questions in this and the next few chapters. 

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