Name: Close Packed Structures and Packing Efficiency
Uploaded: 2019-07-19
Duration: 5 min 51 s
Description: Metals such as copper and silver crystallise in a face-centred cubic (FCC) structure. This type of close packing is often written as ABCABC and is highly eff...

Question

What are

F

-centers?

Accepted Answer

If the number of missing anions is more than cation. So, to maintain electrical neutrality, some electrons are trapped at anionic vacancies. Because of these extra electrons, the electrical and optical properties of the compound get modified. So these locations are known as $F$ -centres.

For example, in NaCl, sodium atoms get deposited on the surface of the crystal when sodium chloride is heated in an atmosphere of sodium vapour. In this process, the chloride ions get diffused with sodium ions and form sodium chloride. In this process, sodium atoms release electrons to form sodium ions. These released electrons get diffused and occupy the anionic sites in the crystal of sodium chloride and creating anionic vacancies that result in the excess of sodium metal. The anionic site occupied by unpaired electrons is called F-centre. They impart yellow colour when visible light falls over the crystal of NaCl, the unpaired electrons present get excited because of the absorption of energy.

What are $F$ -centers?

Important Questions on Solid State

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What are F-centers?

Important Questions on Solid State

Learn and Prepare for any exam you want !

What are $F$ -centers?