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The atoms constitute one unit cell of a face centred cubic crystal are 4.

(c) 4, 1, 2, 3

Correct answer is: (A) Covalent

It means that some of their physical properties show different electrical and optical properties in different directions in the same crystal.

(d) (ii) only

(a) Both A and R are correct and R is the correct explanation of A.

Correct answer is: (A) dipole-dipole interactions

Correct answer is: (B) metallic

Depending upon the nature of intermolecular forces present in the constituent particles, crystalline solids are classified into the following four classes:

i. Molecular solids

ii. Ionic solids

iii. Metallic solids

iv. Covalent solids

As the solid has same value of refractive index along all directions, this means that it is isotropic and hence amorphous. Being an amorphous solid, it would not show a clean cleavage when cut with a knife. Instead it would break into pieces with irregular surfaces.

Correct answer is: (D) In solid state, ionic solids do not conduct electricity.

(a) Both A and R are correct and R is the correct explanation of A.

(a) Both A and R are correct and R is the correct explanation of A.

(c) A and R are correct and R is the correct explanation of A

In covalent solids, the constituents (atoms) are bound together in a three dimensional network entirely by covalent bonds. 

Examples - Diamond, Silicon carbide.

1. In molecular solids, the constituents are neutral molecules. They are held together by weak vander waals forces. 

2. Molecular solids are soft and they do not conduct electricity. 

Eg – Solid CO₂

Hybridisation of carbon atom in diamond is sp³ and that in graphite is sp² . The chemical formula of Buckminster fullerene is C₆₀.

\(\therefore\) 1 mole of C₆₀ contains 60 moles of C.

0.1 mole of C₆₀ will contain 6.0 moles of C.

Weight of C-atoms = Number of moles of C \(\times\) atomic mass of C

= 6.0\(\times\)12

= 72.0 g

= 0.072 kg

\(\therefore\) 0.1 mole of Buckminster fullerene contains 0.072 kg of carbon.

Correct answer is: (C) anisotropy

Option : (a) p-block elements

FeO is the metal deficiency defect.

Silicon carbide is very hard. It is a covalent solid contains the atoms which are bound together in a three dimensional network entirely by covalent bonds. So the covalent network crystal SiC is very hard and have high melting point.

(a) Both A and R are correct and R is the correct explanation of A.

(c) non polar molecular solid

Correct answer is: (B) carbon

(d) Both a and c

(b) Covalent solid

Correct answer: (B) Graphite

Correct answer: (D) 1

Correct answer is: (D) Graphite

Correct answer is: (D) 5

For n-type, impurity added to silicon should have more than 4 valence electrons.

Correct answer: (D) 5

(c) Anthracene

1. Molecular crystals

2. Diamond, SiO₂

3. Atomic solids 

4. Amorphous 

5. Isotropy 

6. Anisotropic 

7. Ionic 

8. Covalent 

9. Vander waals forces 

10. Graphite

Option : (b) 5

Option : (a) 3 

Option : (b) 4.83 × 10^-25 kg

1. London forces 

2. dipole-dipole interactions 

3. Soft solids 

4. Metallic 

5. Crystal lattice 

6. Unit cell 

7. Coordination number 

8. Primitive unit cell 

9. Seven 

10. Eight

6 is the coordination number of each atom in a simple cubic unit cell.

Each atom in the comer of the cubic unit cell is shared by 8 unit cells.

Atoms X and Y form bcc crystalline structure. Atom X is present at the corners of the cube Atom Y is present at the centre of the cube.

No of atoms of X in the unit cell = \(\frac{N_c}{8}\,=\frac{8}{8}\) = 1

No of atoms of Y in the unit cell = \(\frac{N_b}{1}\,=\frac{1}{1}\) = 1

Ratio of atoms X : Y = 1 : 1

Hence formula of the compound = XY

An atom present at the body centre belongs to only 1 unit cell.

Correct answer is: (C) gold and copper

Option : (d) 367.6 pm

1. Eight 

2. Two 

3. Four

4. X-ray diffraction analysis 

5. 52.31% 

6. Polonium 

7. 68% 

8. hep or hexagonal close packed 

9. ccp or cubic close packed 

10. hep, ccp

The atoms the face centre is being shared by 2.

(a) 3, 4, 1, 2

Option : (c) 1 : 1.3 : 1.4

The coordination number of CSCI is 8 .

74% is the packing efficiency in fcc unit cell.