Solid State Chemistry and Crystal Structure

Packing efficiency in both hexagonal close packed (hcp) and cubic close pakded (ccp) lattices is 74%.

Substances like MnO showing antiferromagnetism have domain structure similar to ferromagnetic substance, but their domains are oppositely oriented and cancel out each other's magnetic moment

Metal deficiency defect is generally found in NiO.

Crystal system with edge length a ≠ b ≠ c, and axial angles α = β = γ = 90° is orthorhombic crystal system.

Intrinsic semiconductors are semiconductors due to thermal defects. At 0 K, pure Si or Ge act as insulators, however, at higher temperatures, some of the covalent bonds are broken and the electrons so released become free to move in the crystal and thus, conduct electricity. Extrinsic semiconductors are semiconductors due to impurity defects. Si and Ge (group 14 elements) in pure state have very low electrical conductivity. Their electrical conductivity can be enhanced by the addition of traces of elements belonging to group 13 and 15. Introduction of group 13 or 15 elements to the crystal lattice of group 14 elements p-type and n-type semiconductors, respectively. The process of adding impurities is called doping.

Correct option. The energy level of the highest occupied orbital in a metal at absolute zero is called Fermi level.

Correct option; crystalline solids have definite heat of fusion, so they have a sharp melting point also.

Correct answer. Packing efficiency of BCC lattice structure is 68%.

(NH₄)₃PO₄ and LiBr both are ionic solids.

In simple cubic lattice, participation of each atom is 1/8.

Correct answer.
MgAl₂O₄ crystallises to form spinel structure.
FeTiO₃ crystallises to form ilmenite structure.
CaTiO₃ crystallises to form perovskite structure.
TiO₂ crystallises to form rutile structure.

Correct option. The number of nearest neighbours of a particle is called its coordination number. Coordination number of atoms in BCC crystal lattice is 8.

Frenkel defect leads to no change in density, but Schottky leads to decrease in density.
N-type semiconductor is the result of doping of group 15 into group 14.

Correct option; Except 1, 3, and 4, all are incorrect statements.
A fully occupied band separated from the next (empty) band by a large energy separation (the band gap) leads to the material being an insulator.
A band gap occurs when there is some energy difference between two bands.
Electrical conductivity is a characteristic property of partially filled bands of MOs.
Overlapping of both bands leads to the material being metallic.
Large energy gap between bands leads to the material being insulator.

Crystal systems are differentiated on the basis of their edge lengths and axial angles. So, option 2 classifies them on this basis.
Monoclinic: a ≠ b ≠ c, α = γ = 90°, β ≠ 90°
Tetragonal: a = b ≠ c, α = β = γ = 90°
Orthorhombic: a ≠ b ≠ c, α = β = γ = 90°
Trigonal: a = b = c, α = β = γ ≠ 90°