Vacancy defect is called a thermodynamic defect because this defect arises due to the absorption of heat from the surroundings.

Graphite is a good conductor of electricity because in each layer every carbon atom is linked to three carbon atoms, the fourth electron is free to move about. Presence of these electrons makes it a good conductor.

Quartz glass is said to be amorphous, and hence a supercooled liquid due to its high viscosity.

Rubber is an amorphous solid as there is no regular arrangement of its constituents particles.

On heating electrons are trapped at the anionic sites forming F-centres, which absorb energy from light and radiate pink colour.

FCC has maximum packaging efficiency, as it has a closed packed structure.

In the molten state, ionic solids dissociate to give free ions, and hence can conduct electricity.

Alkali metals have large size, which cannot fit into the interstitial sites.

The reason behind such magnetic behaviour is that metal ions in these substances are grouped together into domains. Each domain acts as a tiny magnet having a definite magnetic moment.

Increases from 6:6 to 8:8 as NaCl structure gets converted to CsCl structure.

As the smaller ions get dislocated from the normal site to an interstitial site.

As doping is done with electron rich or electron deficient impurities. Hence, it introduces electronic defects.

NaCl has FCC arrangement of Cl ions. Hence, the number of Cl ions in packaging per unit cell= 4 Tetrahedral is double of octahedral voids. Thus, 2n= 8.

Electrical conductivity decreases with an increase of temperature because on heating, the positive ions of the metal atoms start vibrating and produce resistance in the flow of electrons.

Since, no ions are missing from the crystal as a whole, therefore density of the solid remains unchanged.