Consider the following statements
I. NaCl and KCl show metal excess defect due to anionic vacancies
II. F- centres are the anionic site occupied by unpaired electrons
III. F-centres is derived from the germen word farbenzenter for colour centre .
F-centres impart yellow colour to the NaCl crystals
Which of the above statements is / are correct ?

Options

A. II, III and IV
B. I, III and IV
C. I, III and II
D. All of these

Answer

D

Explanation

Alkali metals like KCl and NaCl show metal deficiency defect. Due to loss of unpaired electron, Na changes to `Na^+ " and combine with " Cl^-` to form NaCl These unpaired electrons occupy anionic sites which is called F-centres that imparts yellow colour in the crystal.