Anion Vacancies and F Centres in Metal Excess Defects

The video tutorial explains non-stoichiometric defects in inorganic solids, focusing on metal excess defects caused by anion vacancies. It describes how these vacancies are filled by unpaid electrons, forming F centers that impart color to the crystals. Examples include alkyl halides like sodium chloride and potassium chloride.

What happens to the stoichiometry of a compound when non-stoichiometric defects occur?

• It changes.

• It remains unchanged.

• It becomes less stable.

• It becomes more stable.

Which of the following is a cause of metal excess defects?

• Excess anions

• Anion vacancies

• Excess electrons

• Cation vacancies

In a metal excess defect, what occupies the anion vacancy?

• An unpaired electron

• A paired electron

• A proton

• A cation

What is the term used for the vacant lattice site occupied by an unpaired electron?

• F center

• H center

• G center

• E center

Which of the following compounds is known to exhibit metal excess defects?

• Aluminum oxide

• Magnesium oxide

• Sodium chloride

• Calcium carbonate