If an electron is present in place of an anion in a crystal lattice,then it is called

In the laboratory,sodium chloride is made by burning sodium in an atmosphere of chlorine. The resulting crystal is yellow in color. The cause of this yellow color is:

Explain the following term with a suitable example:
$(ii)$ Frenkel defect

Which of the following does not change the density of $SiC$ solid?

Which is the correct statement?

Which defect causes a decrease in the density of a crystal?