The Solid State

 In ionic solids, constituent particles are held together with strong electrostatic force of attraction along with their fixed position. The fixed position of ions and strong electrostatic force of attraction make ionic solids hard and brittle.

Metal excess defect due to the presence of extra cations at interstitial sites: Zinc oxide is white in colour at room temperature. On heating it loses oxygen and turns yellow

f centres are the anionic vacancies occupied by unpaired electron. since the presence of unpaired electrons shows paramagnetic.

The catalytic activity dependsvery much on the surface area per unit mass of the sample.
Transition metal corresponds show metal deficiency due to absence of metal ion from its lattice. The charge is balanced by an adjacent ion having higher positive charge which ultimately increases chemisorption.