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Option : (c) ABCABC

The no of nearest neighbors of a particle or the no of spheres which are touching a given sphere. 

Voids (Interstitial Voids or Sites or Hole): Free space or vacant between close packed constituent particles. 

Types of voids: 

Tetrahedral void 

Octahedral void 

various types of close packing of constituent particles. 

Close packing in three dimensions

Simple Cubic Lattice or Structure:

• AAA….type arrangement generates simple cubic lattice in three dimension 
• Its unit cell is primitive cubic unit cell. 
• Packing efficiency = 52.4% 

Hexagonal Close Packing Structure (HCP): 

• ABAB….Type arrangement 
• Example: Mg, Zn. 
• Packing efficiency = 74% o Coordination number = 12 
• It has N no of octahedral voids and 2N no. of tetrahedral voids if it has N no. of spheres.

Cubic Close Packing Structure (CCP): 

• ABCABC….Type arrangement 
• CCP structure is also called FCC structure. Example: Ag, Cu. 
• Packing efficiency = 74% 
• Coordination number = 12.
• If there is N no. of close packed spheres then it has 2N no. of tetrahedral voids and N no. of octahedral voids. 

Correct answer is: (D) presence of free electrons

Metallic solids are good conductors but ionic solids are bad conductors of electricity.

Correct answer is: (B) hexagonal

Unit cell dimension of hexagonal crystal

 = a = b \(\neq\) c and \(\alpha\) = \(\beta\) = 90\(^\circ\), \(\gamma\) = 120\(^\circ\)

The magnetic moment is measured in Bohr magneton (μ_B).

The anion sites which are occupied by unpaired electron are called F-centres.

The anion sites which are occupied by unpaired electron are called F-centres.

The colours and paramagnetic behaviour of the solid is due to the presence of F-center in a solid.

When a unit cell contains one or more constituent particles present at positions other than corners in addition to those at corners, it is called a centred unit cell.

Centred unit cells are of three types:

a. Body-centred unit cells: These unit cells contain one constituent particle (atom, molecule or ion) at its body-centre besides the ones present at its corners.

b. Face-centred unit cells: These unit cells contain one constituent particle present at the centre of each face, besides the ones present at its corners.

c. End-centred unit cells: In such a unit cell, one constituent particle is present at the centre of any two opposite faces besides the ones present at its corners.

Option : (c) 217.3 gmol^-1

Correct answer is: (C)\(\cfrac{16}{3}\pi r^3\)

Volume occupied by one atom of radius ‘r’=\(\cfrac{4}{3}\pi r^3.\)

\(\therefore\)In fcc unit cell, there are 4 atoms present.

present in fcc unit cell = \(4\times\cfrac{4}{3}\pi r^3=\cfrac{16}{3}\pi r^3\)

Consequences of Frenkel defect :

• Since there is no loss of ions from the crystal lattice, the density of the solid remains unchanged.
• The crystal remains electrically neutral.
• This defect is observed in ZnS, AgCl, AgBr, AgI, CaF_2, etc.

Correct answer is: (D) All of these

Correct answer is: (A) \(\uparrow\)\(\uparrow\)\(\uparrow\)\(\uparrow\)\(\uparrow\)

(a) 2, 4, 1, 3

(c) molecular solid

Lattice points are occupied by CO₂ molecules

Correct answer is: (A) Fe

Ferromagnetism:- Ferromagnetic substances are those substances which shows permanent magnetism when magnetic field is removed. 

For example:- Fe, CrO₂ 

(ii) Para magnetism:- Paramagnetic substances are those which are attracted by an external magnetic field but they lose their magnetism in the absence of a magnetic field due to the presence of atoms, molecules or ions containing unpaired electrons. 

For example:- Cu²⁺,Fe³⁺,O₂,Cr³⁺ etc. 

(iii) Ferrimagnetism:- Ferrimagnetism substances are those substances in which the magnetic moments are aligned in parallel and anti-parallel directions in unequal numbers resulting in net magnetic moment. 

For example:-Fe₃O₄,Ferrites MgFe₂O₄

(a) Both assertion and reason are true and reason is the correct explanation of assertion

Correct answer: (C) do not undergo clean cleavage when cut with knife

d \(= \cfrac{z.M}{a^3.N_o}\)

where, a is edge of unit cell

N₀ = Avogadro number (6.023 \(\times\) 10²³)

M = Molar mass

z = number of atoms per unit cell

For fcc, z = 4

for bcc, z = 2

for simple cubic, z = 1

Correct answer: (B) super cooled liquid

Correct answer: (A) amorphous solid

Packing efficiency =\(\cfrac{Volume\,occupied\,by\,spheresin\,unit\,cell}{Volume\,of \,unit \,cell}\times100\)

In simple ionic crystals, the cations commonly occupy the voids or holes. The voids are empty spaces left between anionic spheres.

i. Radius Ratio \(\left(\cfrac{r^+}{r^-}\right):\)

The critical radius ratio of the void (cation) and sphere (anion), is calculated by solid geometry.

\(\therefore\) Radius ratio = \(\cfrac{r^+}{r^-}\)\(=\cfrac{Cation\,radius}{Anion\,radius}\)

ii. Coordination Number (CN) :

The number of spheres (atoms, molecules or ions) directly surrounding a single sphere in a crystal, is called coordination number.

Correct answer is: (B) A metal that crystallizes in bcc structure has a coordination number of 12.

A metal that crystallizes in bcc structure has a coordination number of 8.

(c) 32%

In crystal lattice formed by bcc unit cell the void volume is 32%.

Correct answer is

(c) If the number of atoms is N the number of octahedral voids is 2N.

(d) 8

The coordination number of atoms in bcc crystal lattice is 8.

Option : (d) any one of the above three

\(\overrightarrow{AB}\) represents arrangement of identical particles of one type.

\(\overrightarrow{CD}\) represents arrangement of identical particles of another type.

\(\overrightarrow{EF}\) represents regular arrangement of two different particles in alternate positions.

Correct answer is: (C) forbidden zone

Correct answer is: (B) molecular orbital theory

Correct answer is: (B) very high

ȡ = Z x M/a³ x N_A

2.7 = Z x 27/(4.05 x 10^-8 ) ³ x 6.023 x 10²³

Z = 1080.29 x 10^-1 / 27

Z = 4 , FCC 

Correct answer is: (D) Molecular

Correct answer is: (B) Glass

Correct answer is: (A) an intrinsic semiconductor

Correct answer is: (B) semiconductor

Correct answer is: (A) is enhanced

There are three major classes of point defects : stoichiometric point defects, impurity defects and nonstoichiometric point defects.

There are four types of stoichiometric point defects as vacancy defect, self interstitial defect, Schottky defect and Frenkel defect.

The point defects in which the ratio of cations to anions remains the same as shown by the molecular formula of the compound are known as stoichiometric defects.

Types of non - stoichiometric efects: 

Metal excess defect: 

Due to anionic vacancies 

Due to presence of extra cations interstitial sites, Eg. ZnO 

Metal deficiency defect :

Due to cation vacancies. 

Eg. In FeO crystal, some Fe²⁺ cations are missing and extra negative charge is balanced by acquiring extra positive charge by adjacent Fe²⁺ ion to become Fe³⁺ ion.

(a)Ferrimagnetism: The substances in which the magnetic moments of the domains are aligned in parallel and anti-parallel directions, in unequal numbers, are said to have ferrimagnetism. Examples include Fe₃O₄ (magnetite), ferrites such as MgFe₂O₄ and ZnFe₂O₄. 

Ferrimagnetic substances are weakly attracted by a magnetic field as compared to ferromagnetic substances. On heating, these substances become paramagnetic. 

(b) Antiferromagnetism: Antiferromagnetic substanceshave domain structures similar to ferromagnetic substances, but are oppositely-oriented. The oppositely-oriented domains cancel out each other‘s magnetic moments. 

(c) the 13-15 group compounds are prepared by combining group 13 and group15 elements. These compounds are prepared to stimulate average valence of four as in Ge or Si. Indium (III) antimonide (IrSb), aluminium phosphide (AlP), and gallium arsenide (GaAS) are typical compounds of groups 13-15. GaAs semiconductors have a very fast response time and have revolutionised the designing of semiconductor devices.

Correct answer: (C) Triclinic