11.When a cation leaves its normal position in the crystal and moves to some interstitial space, the defect in the crystal is known as

12.What type of defect creates F-centres in the crystal?

13.A crystal may have one or more planes of symmetry as well as one or more than one axis of symmetry but it has only

14.During evaporation of liquid

15.Which of the following is an example of molecular solid?