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1. Similarities: 

• Both ionic and metallic crystals have electrostatic forces of attractiàn. 
• In ionic crystals these forces are between oppositely charged ions. In metals,these forces are among the valence electrons and posityely charged kernels. 
• Both have high melting point.

Differences: 

• Ionic bond is strong due to electrostatic forces of attraction whereas metallic bond may be weak or strong depending upon the number of valence electrons and the size of kernels. 
• In ionic bond, ions are not free to move. Hence, they cannot conduct electricity in solid state. They can do so only in molten state or in aqueous solution. ¡n metals, electrons are free to move. Hence, they conduct electricity in solid state.

2. Ionic crystals are hard due to strong electrostatic forces between them. They are brittle because ionic bond is non – directional.

A solid crystalline electrolyte like NaCl is hard, brittle and electrically nonconductor. But its melt conducts electricity.

Covalent or network solids like SiO₂, (quartz) or SiC or C (diamond).

Each lattice point represents one constituent particle of solid. This constituent particle may be an atom, a molecule (group of atoms) or an ion.

Metallic solids are conductors of electricity, malleable and ductile.

Metallic solids are malleable, ductile and electrical conductors.

1. In ionic crystalline solids, constituent particles are positively charged cations and negatively charged anions placed at alternate lattice points. 

2. The ions are held by strong coulombic electrostatic forces of attraction compensating opposite forces. Hence they are hard. 

3. Since there are no free electrons, they are not malleable and on applying a shearing force, ionic crystals break into small units. Hence they are brittle.

The ionic compounds are very hard and brittle. In ionic compounds the ions are rigidly held in a lattice because the positive and negative ions are strongly attracted to each other and difficult to separate. But the brittleness of a compound is now easy to shift the position of atoms or ions in a lattice.

If we apply a pressure on the ionic compounds the layers shifts slightly. The same charged ions in the lattice comes closer. A repulsive forces arises between ‘ same charged ions, due to this repulsions the lattice structure breaks down chemical bonding.

(a) The constituent particles of ionic crystals are ions. These ions are held together in three-dimensional arrangements by the electrostatic force of attraction. Since the electrostatic force of attraction is very strong, the charged ions are held in fixed positions. This is the reason why ionic crystals are hard and brittle. 

 (b)Copper is a metallic solid and all metallic solids are ductile and malleable.

In amorphous silica, SiO₄ tetrahedral are randomly joined to each other whereas in quartz they are linked in a regular manner.

Schottky defect

Correct answer is: (D) 12

Correct answer is: (A) 52.4%

Correct answer is: (C) increases

Correct answer is: (A) 0.732 – 1.000

Correct answer is: (D) 12

Correct answer is: (C) 6

Correct answer is: (D) 4

In tetrahedral voids four spheres are involved in its formation.

Correct answer is: (D) 0.225 - 0.414

Correct answer is: (C) 2N

Molecular solids: water, argon.

Ionic solids: potassium sulphate, zinc sulphate.

Metallic solids: tin, rubidium.

Covalent or network: benzene, urea, ammonia, graphite, silicon carbide.

Since Cu₂O is non-stoichiometric oxide, it contains Cu in two oxidation states, +1 and +2. Cu²⁺ provides an excess of positive charge. As a result an electron from a neighboring Cu⁺ is transferred to Cu²⁺. The transfer of electron leaves behind a hole, which carries an extra positive charge and a negative hole is created. It appears that the positive hole moves through the lattice, hence it appears as P-type semiconductor.

The ratio is less than 2:1 in Cu₂O shows that some cuprous(Cu⁺) ions have been replaced by cupric (Cu²⁺) ions. To maintain electrical neutrality, every two Cu⁺ ions will be replaced by one Cu²⁺ ion thereby creating a’ hole. As conduction will be due to presence of these positive hole, hence it is a p-type semiconductor.

Option : (a) AAAA

1. It is because its conductance is intermediate between conductor and insulator. 

2. In Schottky defect, both cations and anions are missing which leads to lowering the density of a solid.

p-type semiconductor.

Correct answer is:(C) \(\cfrac{1}{2}\) a : \(\cfrac{\sqrt{3}}{4}\) a : \(\cfrac{1}{2\sqrt{2}}a\)

Simple unit cell, r = a / 2

Body centered unit cell, r = \(\cfrac{a\sqrt{3}}{4}\)

Face centered unit cell, r =\(\cfrac{a}{2\sqrt{2}}\)

correct answer is: (C) octahedral

Suppose number of atom B in hcp = N

No. of Tetrahedral void = 2N

Atom A occupying tetrahedral void = 2/3* 2N

Ratio   A:B   A₄B₃

Correct answer is: (A) Diamond

Correct answer is: (D) covalent bonding

Higher the melting points, greater will be the forces of attraction between the molecules or constituent particles and hence greater will be the stability. The melting points of given compounds are as follows.
Water            = 273 K
Ethyl alcohol = 155.7 K
Diethyl ether = 156.7K
Methane       = 90.5 K
The inter molecular forces of attraction between the molecules of water and ethyl alcohol are mainly due to hydrogen bonding. The melting point of water is higher than ethyl alcohol shows that hydrogen bonding in ethyl alcohol molecules is not as strong as in water molecules. Diethyl ether is a polar molecule. The inter molecular forces present in them are dipole-dipole interactions Methane is a non-polar molecule. The only forces present in them are the weak vander waals forces i.e., London dispersion forces.

Amorphous solids have a tendency to flow. Since glass is an amorphous solid , so it is called super cooled liquid or pseudo solid. 

As the solid have same values of refractive index among all directions, it means it is isotropic in nature. Hence, the solid is amorphous. As the solid is amorphous in nature so it would not show clean cleavage when cut with a knife. It would break in to pieces with irregular surfaces.

Glass is an amorphous solid. Like liquid it has a tendency to flow, though very slowly. Because of its flowing nature the glass panes in the windows of old buildings are found to be slightly thicker at the bottom than at the top. Hence glass is consider as super-cooled liquid because of its flowing nature.

Amorphous solids-Polyurethane, Teflon, Cellophane, Polyvinyl chloride, Fibre glass. Crystalline solids-Naphthalene, Benzoic acid, Potassium nitrate and Copper.

In solids the positions of constituent particles like atoms or molecules or ions are fixed i.e., they are not free to move. They are stationary in their fixed position. They have strong intermolecular or interionic forces of attraction. Hence solids are hard.

The answer is (d) 12,6.

Correct answer: (C) 2n, n

Number of atoms in 0.5 mole of compound
= 0.5 x 6.022 x 10²³
= 3.011 x 10²³
Number of octahedral voids = Number of atoms in close packing
= 3.011 x 10²³
Number of terahedral voids = 2 x No. of atoms in close packing
= 2 x 3.011 x 10²³
= 6.022 x 10²³
Total number of voids = 3.011 x 10²³ + 6.022 x 10²³
= 9.033 x 10²³

Correct answer: (B) 12

Correct answer: (B) octahedral void

Correct answer is: (D) 78.54 %

a\(\sqrt{2}\) = 4r

\(\Rightarrow\) a = 2\(\sqrt{2}\) r

Packing fraction =\(\cfrac{Occupied\,area}{Total\,area}\)

\(=\cfrac{2\pi r^2}{(2\sqrt{2r})^2}\times100=78.5\)%

Number of atom in the close packing = 0.5 x 6.023 x 10²³ = 3.011 x 10²³

Number of octahedral void = 1 x 3.011 x 10²³ 

Number of tetrahedral void 2 x 3.011 x 10²³

= 6.033 x 10²³ 

Correct answer is: (B) octahedral void

(a) a = 2r 

(b) a = 4 r 

(c) a = 2 2r

The relationship between atomic radius (r) and edge length (a) in the bcc unit cell are r = √3a/2

Relationship between edge length of unit cell (a) and radius of sphere(r): 

Type of Stoichiometric defects: 

Vacancy defects: 

(i) some of the lattice sites of the crystal are vacant. 

(ii) This defect decreases the density of the crystal. 

(iii) This defect can be developed by heating the substance. 

Interstitial defects: 

(i) some constituent particles occupy the interstitial sites of the crystal. 

(ii) This defect increases the density of the crystal. 

Correct answer is: (C) combination of Si doped with As and B