Additional Questions - Chapter 6 - Solid State - 12th Chemistry Guide Samacheer Kalvi Solutions

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Additional Questions
1 Mark Questions and Answers
I. Choose the best answer.
Question 1.
Consider the following statements
(i) Solids have definite volume and shape
(ii) Solids are rigid and compressible
(iii) Solids have weak cohesive forces
Which of the above statemetns is / are not correct?
(a) (i) only
(b) (ii) \& (iii) only
(c) (iii) only
(d) (i) \& (ii) only
Answer:
(b) (ii) \& (iii) only
Question 2.
Which one of the following is an ionic crystal?
(a) Glass
(b) Rubber
(c) $\mathrm{NaCl}$
(d) $\mathrm{SiO}_2$
Answer:
(c) $\mathrm{NaCl}$
Question 3.
Which one of the following is an amorphous solid?
(a) Glass
(b) $\mathrm{SiO}_2$
(c) $\mathrm{NaCl}$
(d) $\mathrm{Na}$
Answer:
(a) Glass

Question 4.
Which one of the following is an example for molecular crystals?
(a) Diamond
(b) Silica
(c) Glass
(d) Naphthalene
Answer:
(d) Naphthalene
Question 5 .
Which one of the following is an example for atomic solids?
(a) Frozen elements of group 18
(b) Group 17 elements
(c) Inner - transition elements
(d) chalcogens
Answer:
(a) Frozen elements of group 18
Question 6.
Which one of the following is a covalent crystal?
(a) Glass
(b) Diamond
(c) Anthracene
(d) Glucose
Answer:
(b) Diamond
Questions 7.
Consider the following statements.
(i) Crystalline solids have irregular shape
(ii) Generally crystalline solids are anisotropic in nature
(iii) Heat of fusion of crystalline solids are not definite
Which of the above statements is / are correct?
(a) (i) \& (iii)
(b) (i) only
(c) (iii) only
(d) (ii) only
Answer:
(d) (ii) only

Question 8.
Consider the following statements.
(i) Amorphous solids are isotropic like liquids
(ii) Amorphous solids are considered as pseudo solids
(iii) Amorphous solids have sharp melting points
Which of the above statemetns is / are correct?
(a) (i) only
(b) (ii) only
(c) (i) \& (ii)
(d) (i) \& (iii)
Answer:
(c) (i) \& (ii)
Question 9.
In an ionic crystal, both cations and anions are bound together by
(a) Strong electrostatic attractive forces
(b) Weak electrostatic attractive forces
(c) Vanderwaals forces of attraction
(d) Weak cohesive forces
Answer:
(a) Strong electrostatic attractive forces
Question 10.
Molecular solids contains neutral molecules held together by
(a) strong cohesive forces
(b) weak vanderwaals forces
(c) weak ionic forces
(d) strong electrostatic forces
Answer:
(b) weak vanderwaals forces
Question 11.
Which is used inside pencils and in many lubricants?
(a) Lead nitrate
(b) charcoal
(c) graphite
(d) coke
Answer:
(c) graphite
Question 12 .
In non polar molecular solids, molecules are held together by
(a) London forces
(b) weak vanderwaals forces
(c) Strong electrostatic forces
(d) strong cohesive forces
Answer:
(a) London forces

Question 13.
Which one of the following is non-polar molecular solids?
(a) Diamond
(b) $\mathrm{SiC}$
(c) Anthracene
(d) Glass
Answer:
(c) Anthracene
Question 14.
Silicon carbide is an example of
(a) Ionic solid
(b) Covalent solid
(c) Polar molecular solid
(d) Non-polar molecular solid
Answer:
(b) Covalent solid
Question 15 .
Naphthalene is an example of .
(a) ionic solid
(b) covalent solid
(c) non polar molecular solid
(d) polar molecular solid
Answer:
(c) non polar molecular solid
Question 16.
Solid $\mathrm{NH}_3$ solid $\mathrm{CO}_2$ are examples of
(a) Covalent solids
(b) polar molecular solids
(c) molecular solids
(d) ionic solids
Answer:
(b) polar molecular solids
Question 17.
Solids ice, glucose are examples of
(a) metallic solids
(b) ionic solids
(c) hydrogen bonded molecular solids
(d) non polar molecular solids
Answer:
(c) hydrogen bonded molecular solids

Question 18.
Consider the following statements.
(i) metallic solids possess high electrical and thermal conductivity
(ii) solid ice are soft solids under room temperature
(iii) In non polar molecular solids constituent molecules are held together by strong electrostatic forces of attraction
Which of the above statements is / are not correct?
(a) (i) \& (ii)only
(b) (iii) only
(c) (ii) only
(d) (i) only
Answer:
(b) (iii) only
Question 19.
Each atom in the comer of the cubic unit cell is shared by how many unit cells?
(a) 8
(b) 6
(c) 1
(d) 12
Answer:
(a) 8
Question 20.
Which is the coordination number of each atom in a simple cubic unit cell?
(a) 8
(b) 6
(c) 12
(d) 4
Answer:
(b) 6
Question 21 .
The number of atoms belongs to fcc unit cell is
(a) 2
(b) 4
(c) 6
(d) 12
Answer:
(a) 2

Question 22 .
The number of atoms in fee unit cell is
(a) 2
(b) 4
(c) 6
(d) 8
Answer:
(b) 4
Question 23.
The atoms the face centre is being shared by
(a) 4
(b) 8
(c) 2
(d) 6
Answer:
(c) 2
Question 24.
An atom present at the body centre be longs to only unit cell
(a) 1
(b) 2
(c) 4
(d) 8
Answer:
(a) 1
Question 25.
Which one of the following is known as Bragg's equation'?
(a) $\mathrm{d}=\frac{2 \sin \theta}{n \lambda}$
(b) $\mathrm{d}=\frac{n \lambda}{2 \sin \theta}$
(c) $\mathrm{d}=\frac{d}{\sin \theta}$
(d) $\mathrm{d}=\frac{2 \sin \theta}{n \lambda}$
Answer:
(b) $\mathrm{d}=\frac{n \lambda}{2 \sin \theta}$

Question 26.
Which one of the following formula is used to calculate the density of the unit cell?
(a) $\rho=\frac{n M}{a^3 N_A}$
(b) $\rho=\frac{a^3 N_A}{n M}$
(c) $\rho=\frac{N_A}{a^3 N M}$
(d) $\rho=\frac{a^3 N_A}{n}$
Answer:
(a) $\rho=\frac{n M}{a^3 N_A}$
Question 27.
Which is the packing fraction in simple cubic unit cell?
(a) $52.31 \%$
(b) $100 \%$
(c) $68 \%$
(d) $75 \%$
Answer:
(a) $52.31 \%$
Question 28 .
The packing fraction in bcc arrangement is
(a) $52.31 \%$
(b) $68 \%$
(c) $100 \%$
(d) $80 \%$
Answer:
(b) $68 \%$
Question 29.
Which is the coordination number in both hep and ccp arrangements?
(a) 12
(b) 6
(c) 4
(d) 8
Answer:
(a) 12

Question 30 .
What is the coordination number of $\mathrm{B}_2 \mathrm{O}_3$ ?
(a) 4
(b) 6
(c) 8
(d) 3
Answer:
(d) 3
Question 31.
Which one of the following is the structure of $\mathrm{B}_2 \mathrm{O}_3$ ?
(a) Tetra hedral
(b) Octahedral
(c) Trigonal planar
(d) Cubic
Answer:
(c) Trigonal planar
Question 32 .
The coordination number of zinc sulphide is
(a) 3
(b) 4
(c) 6
(d) 8
Answer:
(b) 4
Question 33.
The coordination number of CSCI is ..........
(a) 3
(b) 4
(c) 6
(d) 8
Answer:
(d) 8
Question 34.
Which one of the following is the coordination number of $\mathrm{NaCl}$ ?
(a) 3
(b) 4
(c) 6
(d) 8
Answer:
(c) 6

Question 35 .
Which one of the following is the packing efficiency in fcc unit cell?
(a) $74 \%$
(b) $52.61 \%$
(c) $100 \%$
(d) $68 \%$
Answer:
(a) $74 \%$
Question 36.
Which one of the following is an example for schoriky defect?
(a) $\mathrm{NaCI}$
(b) $\mathrm{AgBr}$
(c) $\mathrm{KCI}$
(d) $\mathrm{FeS}$
Answer:
(a) $\mathrm{NaCl}$
Question 37.
Which one of the following is an example for Frenkel defect?
(a) $\mathrm{NaCl}$
(b) $\mathrm{AgCI}$
(c) $\mathrm{AgBr}$
(d) $\mathrm{AgNO}_3$
Answer:
(c) $\mathrm{AgBr}$
Question 38.
Metal excess defect is possible in ..........
(a) $\mathrm{AgCI}$
(b) $\mathrm{AgBr}$
(c) $\mathrm{KCl}$
(d) Fes
Answer:
(c) $\mathrm{KCl}$

Question 39 .
Which one of the following is the metal deficiency defect?
(a) $\mathrm{FeO}$
(b) $\mathrm{ZnO}$
(c) $\mathrm{KCl}$
(d) $\mathrm{NaCl}$
Answer:
(a) $\mathrm{FeO}$
Question 40 .
Which one of the following shows non-stoichiometric defect?
(a) $\mathrm{FeO}$
(b) $\mathrm{AgBr}$
(c) $\mathrm{ZnO}$
(d) Both a and c
Answer:
(d) Both a and c
II. Fill in the blanks
1. Naphthalene,Anthracene and glucose are examples of ..............
2. The best examples of covalent crystals are .................... and ..................
3. Frozen elements of group 18 are called .......................
4. Glass, Rubber, plastics are the examples of ......................... solids.
5. ......................... means uniformity in all directions.
6. Crystalline solids are ........................... and they show different values of physical properties when measured along different directions.

7. $\mathrm{NaCl}$ and $\mathrm{KCl}$ are the examples of ....................... crystals.
8. Diamond and silicon carbide are the examples of ...................... solids.
9. In molecular solids, the neutral molecules are held together by weak ......................
10 ........... is a component of many lubricants for example cycle chain oil.
11. In non polar molecular solids constituent molecules are held together by ..........................
12. In solids $\mathrm{CO}_2$ solid $\mathrm{NH}_3$ the molecules are held together by strong ........................
13. Glucose and urea are generally under ..................... room temperature.
14. ....................... solids possess excellent electrical and thermal conductivity.
15. The regular arrangement of the ions throughout the crystal is called a .................
16. The basic repeating structural unit of a crystalline solid is called a ................
17. The number of the nearest neighbours that surrounding a particle in a crystal is called the ...................
18. A unit cell that contains only one lattice point is called a ............................
19. There are ................. primitive crystal systems.
20. The coordination number of bcc is .......................
21. Each atom in the comer of cubic unit cell is shared by ...................... neighbouring unit cells.
22. The number of atoms in bcc unit cell is ....................
23. The number of atoms in a fee unit cell is ......................
24. ..................... is the most powerful tool for the determinaiton of crystal structure.
25. Only  .......................... of the available volume is occupied by the spheres in simple cubic packing
26. Of all the metals in the periodic table, only ..................... crystallizes in simple cubic pattern.
27. In bcc cubic pattern .................... of the available volume is occupied.
28. If the third layer arrangement is aba arrangement, it is called ..................... arrangement.
29. If third layer arrangement is abc arrangment, it is known as ......................... arrangement.
30. In both......................... and ............................. arrangements, the coordination number of each sphere is 12 .
31. The packing efficiency of fee unit cell is .........................
32. .......... defect arises due to the missing of equal number of cations and anions from the crystal lattice.
33. Presence of large number of schottky defects in a crystal, lowers its ...................
34. Vanadium monoxide shows ....................... defect.
35. ................. arises due to the dislocation of ions from its crystal lattice.
36. ....................arises due to the presence of more number of metalions as compared to anions.
37. $\mathrm{Zno}$ is ........................ at room temperature but when it is heated it becomes in colour.
38. ...................... arises due to the presence of less number of cations than the anions.
39. ........................... is the appearance of an electrical potential across the sides of the crystal, when it is subjected to mechanical stress.
40. Stoichiometric defects in an ionic solid is also called .............................. or ..................... defect.

Answer:
1. Molecular crystals
2. Diamond, $\mathrm{SiO}_2$
3. Atomic solids
4. Amorphous
5. Isotropy
6. Anisotropic
7. Ioni
8. Covalent
9. Vander waals forces
10. Graphite
11. London forces
12. dipole-dipole interactions
13. Soft solids
14. Metallic
15. Crystal lattice
16. Unit cell
17. Coordination number
18. Primitive unit cell
19. Seven
20. Eight
21. Eight
22. Two
23. Four
24. X-ray diffraction analysis
25. $52.31 \%$
26. Polonium
27. $68 \%$
28. hep or hexagonal close packed
29. ccp or cubic close packed
30. hep, ccp
31. $74 \%$
32. Schottky
33. density
34. Schottky defect
35. Frenkel defect
36. metal excess defect
37. Colourless, yellow
38. Metal deficiency
39. Piezoelectricity
40. intrinsic or thermodynamic

III. Match the following:
Question 1.

Answer:
(a) $3,4,1,2$
Question 2.

Answer:
(b) $3,1,4,2$
Question 3.

Answer:
(a) 2, 4, 1, 3
Question 4.

Answer:
(b) $3,1,4,2$
Question 5.

Answer:
(c) $4,1,2,3$
IV. Assertion and Reason
Question 1.
Assertion (A): Amorphous solids are isotropic in nature.
Reason (R): In amorphous solids, they have identical values of physical properties such as refractive index, electrical conductance in all directions which is called isotropy.
(a) Both $\mathrm{A}$ and $\mathrm{R}$ are correct and $\mathrm{R}$ is the correct explanation of $\mathrm{A}$.
(b) Both $\mathrm{A}$ and $\mathrm{R}$ are correct but $\mathrm{R}$ is not the correct explanation of $\mathrm{A}$
(c) $A$ is correct but $R$ is wrong
(d) $\mathrm{A}$ is wrong but $\mathrm{R}$ is correct
Answer:
(a)Both $\mathrm{A}$ and $\mathrm{R}$ are correct and $\mathrm{R}$ is the correct explanation of $\mathrm{A}$.
Question 2.
Assertion (A): Crystalline solids are anisotropic in nature.
Reason (R): Anisotropy is the property which depends on the direction of measurement. Crystalline solids are anisotropic and they show different values of physical properties when measured along different directions.
(a) Both $\mathrm{A}$ and $\mathrm{R}$ are correct and $\mathrm{R}$ is the correct explanation of $\mathrm{A}$.
(b) Both $\mathrm{A}$ and $\mathrm{R}$ are correct but $\mathrm{R}$ is not the correct explanation of $\mathrm{A}$
(c) $\mathrm{A}$ is correct but $\mathrm{R}$ is wrong
(d) $\mathrm{A}$ is wrong but $\mathrm{R}$ is correct
Answer:
(a)Both $\mathrm{A}$ and $\mathrm{R}$ are correct and $\mathrm{R}$ is the correct explanation of $\mathrm{A}$.
Question 3.
Assertion (A): Ionic solids do not conduct electricity in solid state but in molten state they conduct electricity. Reason (R): In solid state, the ions are fixed in their lattice positions but in molten state, the ions are free to move and conduct electricity.
(a) Both $\mathrm{A}$ and $\mathrm{R}$ are correct but $\mathrm{R}$ is not correct explanation of $\mathrm{A}$.
(b) Both $\mathrm{A}$ and $\mathrm{R}$ are correct and $\mathrm{R}$ is the correct explanation of $\mathrm{A}$
(c) $A$ is correct but $R$ is wrong
(d) $\mathrm{A}$ is wrong but $\mathrm{R}$ is correct
Answer:
(A)Both A and $\mathrm{R}$ are correct and $\mathrm{R}$ is the correct explanation of $\mathrm{A}$

Question 4.
Assertion (A): Diamond and Silicon carbide are very hard and have high melting point.
Reason (R): In covalent solids, the atoms are bound together in a three dimensional network entirely by covalent bonds.
(a) Both $\mathrm{A}$ and $\mathrm{R}$ are correct and $\mathrm{R}$ is the correct explanation of $\mathrm{A}$.
(b) Both $\mathrm{A}$ and $\mathrm{R}$ are correct but $\mathrm{R}$ is not the correct explanation of $\mathrm{A}$
(c) $A$ is correct but $R$ is wrong
(d) $\mathrm{A}$ is wrong but $\mathrm{R}$ is correct
Answer:
(a)Both $\mathrm{A}$ and $\mathrm{R}$ are correct and $\mathrm{R}$ is the correct explanation of $\mathrm{A}$.
Question 5.
Assertion (A): Solid $\mathrm{CO}_2$ Solid $\mathrm{NH}_3$ have higher melting points.
Reason (R): The constituents are molecules formed by polar covalent bonds. They are held together by relatively strong dipole- dipole interactions.
(a) $\mathrm{A}$ is correct but $\mathrm{R}$ is wrong.
(b) $\mathrm{A}$ is wrong but $\mathrm{R}$ is correct
(c) $\mathrm{A}$ and $\mathrm{R}$ are correct and $\mathrm{R}$ is the correct explanation of $\mathrm{A}$
(d) $\mathrm{A}$ and $\mathrm{R}$ are correct but $\mathrm{R}$ is not the correct explanation of $\mathrm{A}$
Answer:
(c) $\mathrm{A}$ and $\mathrm{R}$ are correct and $\mathrm{R}$ is the correct explanation of $\mathrm{A}$
Question 6.
Assertion (A): Solid ice, Glucose are generally soft solids under room temperature.
Reason (R): The constituents are held together by strong electrostatic forces of attraction.
(a) Both $\mathrm{A}$ and $\mathrm{R}$ are correct and $\mathrm{R}$ is the correct explanation of $\mathrm{A}$
(b) Both $\mathrm{A}$ and $\mathrm{R}$ are correct and $\mathrm{R}$ is not the correct explanation of $\mathrm{A}$
(c) $\mathrm{A}$ is correct but $\mathrm{R}$ is wrong.
(d) $\mathrm{A}$ is wrong but $\mathrm{R}$ is correct
Answer:
(c) $\mathrm{A}$ is correct but $\mathrm{R}$ is wrong.
Question 7.
Assertion (A): In bcc, the available volume is more efficiently used than in simple cubic packing.
Reason (R): In simple cubic arrangement, the number of spheres belongs to a unit cell is equal to one whereas in bcc, it is equal to 2 .
(a) Both $\mathrm{A}$ and $\mathrm{R}$ are correct and $\mathrm{R}$ is the correct explanation of $\mathrm{A}$
(b) Both $\mathrm{A}$ and $\mathrm{R}$ are correct $\mathrm{R}$ is not the correct explanation of $\mathrm{A}$
(c) $\mathrm{A}$ is correct but $\mathrm{R}$ is wrong.
(d) $\mathrm{A}$ is wrong but $\mathrm{R}$ is correct
Answer:
(a) Both $\mathrm{A}$ and $\mathrm{R}$ are correct and $\mathrm{R}$ is the correct explanation of $\mathrm{A}$

Question 8.
Assertion (A): $\mathrm{B}_2 \mathrm{O}_3$ has trigonal planar structure.
Reason (R): The ratio of radius of cation and anion $\frac{r_{c^{+}}}{r_{A^{-}}}=0.155-0.225$ plays an important role in determining the structure . and $\mathrm{B}_2 \mathrm{O}_3$ has coordination number as 3 and has trigonal planar structure.
(a) Both $\mathrm{A}$ and $\mathrm{R}$ are correct and $\mathrm{R}$ is the correct explanation of $\mathrm{A}$
(b) Both $\mathrm{A}$ and $\mathrm{R}$ are correct but $\mathrm{R}$ is not the correct explanation of $\mathrm{A}$
(c) $\mathrm{A}$ is correct but $\mathrm{R}$ is wrong.
(d) $\mathrm{A}$ is wrong but $\mathrm{R}$ is correct
Answer:
(a) Both $\mathrm{A}$ and $\mathrm{R}$ are correct and $\mathrm{R}$ is the correct explanation of $\mathrm{A}$
Question 9.
Assertion (A): Schottky defect does not change the stoichiometry of the crystal.
Reason (R): This defect arises due to the missing of equal number of cations and anions from the crystal lattice.
(a) Both $\mathrm{A}$ and $\mathrm{R}$ are correct but $\mathrm{R}$ is not the correct explanation of $\mathrm{A}$
(b) Both $\mathrm{A}$ and $\mathrm{R}$ are correct and $\mathrm{R}$ is the correct explanation of $\mathrm{A}$
(c) $\mathrm{A}$ is correct but $\mathrm{R}$ is wrong.
(d) $\mathrm{A}$ is wrong but $\mathrm{R}$ is correct
Answer:
(a) Both $\mathrm{A}$ and $\mathrm{R}$ are correct and $\mathrm{R}$ is the correct explanation of $\mathrm{A}$
Question 10 .
Assertion (A): Zinc oxide is colourless at room temperature but on heating it becomes yellow in colour.
Reason $(\mathrm{R})$ : On heating Zinc loses oxygen and thereby forming free $\mathrm{zn}^{2+}$ ions. The excess $\mathrm{zn}^{2+}$ ions move to interstitial sites and the electrons also occupy interstitial positions.
(a) Both $\mathrm{A}$ and $\mathrm{R}$ are correct and $\mathrm{R}$ is the correct explanation of $\mathrm{A}$
(b) Both $\mathrm{A}$ and $\mathrm{R}$ are correct $\mathrm{R}$ is not the correct explanation of $\mathrm{A}$
(c) $A$ is correct but $R$ is wrong.
(d) $A$ is wrong but $R$ is correct
Answer:
(a) Both $\mathrm{A}$ and $\mathrm{R}$ are correct and $\mathrm{R}$ is the correct explanation of $\mathrm{A}$
V. Find the odd one out
Question 1.
(a) Plastic
(b) Rubber
(c) Glucose
(d) Glass
Answer:
(c) Glucose It is a molecular solid where as others are amorphous solids.

Question 2 .
(a) Anthracene
(b) Naphthalene
(c) Glucose
(d) Sodium chloride
Answer:
(d) Sodium chloride It is ionic crystall where as others are molecular crystals.
Question 3.
(a) Sodium
(b) Pottasium
(c) Frozen elements of group 18
(d) Gold
Answer:
(c) Frozen elements of group 18 It is atomic solid where as others are metallic solids.
Question 4.
(a) Solid $\mathrm{CO}_2$
(b) Solid ice
(c) Glucose
(d) Urea
Answer:
(a) Solid $\mathrm{CO}_2$ It is a polar molecular solid where as others are hydrogen bonded molecular solids.
Question 5
(a) Cubic
(b) Rhombohedral
(c) Hexagonal
(d) Cyclic
Answer:
(d) Cyclic It is a ring structure where as other primitive crystal systems.
VI. Find the odd correct pair
Question 1.
(a) Glass, plastic
(b) Rubber, ice
(c) Nacl, Glucose
(d) Urea, solid $\mathrm{NH}_3$
Answer:
(a) Glass, plastic (Amorphous solids)

Question 2.
(a) $\mathrm{NaCI}, \mathrm{KCI}$
(b) $\mathrm{FeO}, \mathrm{ZnO}$
(e) $\mathrm{AgBr}, \mathrm{AgNO}_3$
(d) $\mathrm{VO}, \mathrm{ZnO}$
Answer:
(a) Naci, Kcl (schottky defect)
Question 3.
(a) Solid $\mathrm{CO}_2$ Solid ice
(b) Solid $\mathrm{CO}_2$ Solid $\mathrm{NH}_3$
(c) Graphite, Silicon carbide
(d) Naphthalene, Phenol
Answer:
(b) Solid $\mathrm{CO}_2$ Solid $\mathrm{NH}_3$ Polar molecular solids
Question 4.
(a) $\mathrm{NaCI}, \mathrm{SiC}$
(b) Naphthalene, anthracene
(c) Solid ice, graphite
(d) Copper, KO
Answer:
(b) Naphthalcne, anthracenc - It is non-polar molecular solid examples.
VII. Find out the odd incorrect pair
Question 1.
(a) $\mathrm{NaCl}, \mathrm{KCl}$
(b) Naphthalenc, anthracene
(c) Solid $\mathrm{CO}_2$, Solid $\mathrm{NH}_3$
(d) Diamond, solid ice
Answer:
(d)Diamond, solid ice

Question 2.
(a) $\mathrm{Cu}, \mathrm{Fc}$
(b) Glucose, Urca
(c) Diamond, $\mathrm{SiC}$
(d) Benzene, glucose
Answer:
(d) Benzene, glucose
2 Mark Question and Answers
Question 1.
What are crystalline solid? Give example.
Answer:
A crystalline solid is one in which its constituents (atoms, ions or molecules) have an orderly arrangement extending over a long range which has three dimensional pattern. Example $-\mathrm{NaCl}$.
Question 2.
What are amorphous solid? Give example.
Answer:
In an amorphous solid, the constituents are randomly arranged. It is a short range arrangement of constituents. Eg - Glass.
Question 3.
What are covalent solids? Give example.
Answer:
In covalent solids, the constituents (atoms) are bound together in a three dimensional network entirely by covalent bonds. Examples. Diamond, Silicon carbide.
Question 4.
Silicon carbide is very hard. Justify this statement.
Answer:
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 $\mathrm{SiC}$ is very hard and have high melting point.
Question 5.
Write a note about molecular solids.
Answer:
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 $-\mathrm{Solid}^{\mathrm{CO}_2}$

Question 6.
What are non-polar molecular solids? Give example.
Answer:
1. In non polar molecular solids, constituent molecules are held together by weak dispersion forces or London forces.
2. They have low melting points and are usually in liquids or gaseous state at room temperature. Eg., Naphthalene, anthrancene.
Question 7.
What are hydrogen bonded molecular solids? Give example.
Answer:
1. Molecular solids in which the constituents are held together by hydrogen bonds.
2. They are generally soft solids under room temperature. Examples., Solid ice, Glucose, Urea.
Question 8.
Define crystal lattice.
Answer:
The regular arrangement of these species throughout the crystal is called a crystal lattice.
Question 9.
Define coordination number.
Answer:
1. A crystal may be considered to consist of large number of unit cells, each one in direct contact with its nearer neighbour and all similarly oriented in space.
2. The number of the nearest neighbours that surrounding a particle in a crystal is called coordination number of that particle.
Question 10.
Draw the tetragonal crystal systems.
Answer:

Question 11.
Draw the hexagonal primitive crystal structure.
Answer:

Question 12.
Draw the typec of monoclinic primitive cubic crystals. Answer:

Question 13.
Draw the primitive cubes.
1. trigonal
2. triclinic
Answer:

Question 14.
What is Bragg's equation?
Answer:
1. X-ray diffraction analysis is the most powerful tool fiw the determination of crystal structure.
2. The interplanar distance (d) between two successive planes of atoms can be calcuLated using the following equation form the X-ray diffraction data $2 \mathrm{~d} \sin \theta=\mathrm{n} \lambda$. The equation is known as Bragg's equation.

Where $\lambda=$ wavelength of $\mathrm{X}$-ray $-\mathrm{d}=$ Interplanar distance, $\theta$ The angle of diffraction $-\mathrm{n}=$ order of reflection. By knowing the values of $\theta, \lambda$ and $\mathrm{n}$. we can calculate the value of $\mathrm{d}$. $\mathrm{d}=\frac{n \lambda}{2 \operatorname{Sin} \theta}$ Using these values, the edge of the unit cell can be calculated.
Question 15 .
What is meant by linear arrangement of spheres in one direction?
Answer:
1. In a specific direction, there is only one possibility to arrange the spheres in one direction.

2. In this arrangement, each sphere is in contact with two neighbouring spheres on either.
Question 16.
What is meant by piezo electricity?
Answer:
Piezo electricity is the appearance of an electrical potential across the sides of a crystal. When you subject it to mechanical stress. The word piezo electricity means electricity resulting from pressure and latent heat. Even the inverse is possible which is known as inverse piezo electric effect.
Question 17.
Why are solids rigid?
Answer:
In a solid, the constituent particles are very closely - packed. Hence, the forces of attraction among these particles are very strong, that is why they are rigid.
Question 18.
Why do solids have a definite volume?
Answer:
The constituent particles of a solid have fixed positions and are not free to move i.e., they possess rigidity. That is why they have a definite volume.
Question 19.
Classify the following as amorphous or crystalline solids: Polyurethane, naphthalene, benzoic acid, teflon, potassium nitrate, cellophane, polyvinyl chloride, fibre glass, copper.
Answer:

Amorphous solids: Polyurethane, teflon, cellophane, polyvinyl chloride, fibre glass. Crystalline solids: Benzoic acid, naphthalene, potassium nitrate, copper.
Question 20.
Why is glass considered as super cooled liquid?
Answer:
Glass is an amorphous solid. Like liquids it has a tendency to flow, though very slowly. The proof of this fact is that glass panes in the windows or doors of old buildings are invariably found to be slightly thicker at the bottom than at the top.
Question 21.
Refractive index of a solid is observed to have the same value along all directions. Comment on the nature of this solid. Would it show cleavage property?
Answer:
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.
Question 22.
Classify the following solids in different categories based on the nature of intermolecular forces operating in them: Potassium sulphate, tin, benzene, urea, ammonia, water, zinc sulphide, graphite, rubidium, argon, silicon carbide.
Answer:
1. Potassium sulphate - Ionic
2. Tin-Metallic
3. Benzene-Molecular (non polar)
4. Urea-Molecular (polar)
5. Ammonia - Molecular (hydrogen bonded)
6. Water - Molecular (hydrogen bonded)
7. Zinc Suiphide - Ionic
8. Graphite - Covalent or Network
9. Rubidium - Metallic
10. Argon - Molecular (non polar)
11. Silicon carbide - Covalent or Network
Question 23.
Solid $\mathrm{A}$ is a very hard electrical insulator in solid as well as in molten state, and melts at extremely high temperature. What type of solid is it?
Answer:
Covalent or Network solid like $\mathrm{SiO}_2$ (quartz) or SIC or $\mathrm{C}$ (diamond).
Question 24.
Ionic solids conduct electricity in molten state but not in solid state. Explain.
Answer:
In the molten state, ionic solids dissociate to give free ions and hence can conduct electricity. However in the solid state, as the ions are not free to move but remain held together by strong electrostatic forces of attraction, so they cannot conduct electricity in the solid state.

Question 25.
An element with molar mass $2.7 \times 10^{-2} \mathrm{~kg} \mathrm{~mol}^{-1}$ forms a cubic unit cell with edge length $405 \mathrm{pm}$. If the density is $2.7 \times 10^3 \mathrm{~kg} \mathrm{~m}^{-3}$, what $i$ s the nature of the cubic unit cell?
Answer:
Density
$
\begin{aligned}
& d=\frac{z \times M}{a^3 \times N_A} \quad(\rho)=\frac{n M}{a^3 N_A} \\
& \mathrm{n}=\frac{\rho^{\times} \mathrm{a}^3 \times \mathrm{N}_{\mathrm{A}}}{\mathrm{M}}=\frac{\left(2.7 \times 10^3 \mathrm{~kg} \mathrm{~m}^{-3}\right)\left(4.05 \times 10^{-10} \mathrm{~m}\right)^3\left(6.022 \times 10^{23} \mathrm{~mol}^{-1}\right)}{2.7 \times 10^{-2} \mathrm{~kg} \mathrm{~mol}^{-1}} \\
& =3.99=4 \\
&
\end{aligned}
$
Thus, there are 4 atoms of elements present per unit cell, hence, the cubic unit cell must be facecentred or cubic close - packed (cep).
Question 26.
Ionic solids, which have anionic vacancies due to metal excess defect develop colour. Explain with the help of suitable example.
Answer:
Taking the example of $\mathrm{NaCl}$, when its crystals arc heated in presence of sodium vapour some chloride ion leave their lattice sites to combine with sodium to form $\mathrm{NaCI}$. For this released diffuses into the crystal to occupy the anion vacancies created by $\mathrm{Cl}$ ions.
The crystal now has excess of sodium. The sites occupied by unpaired electrons are called $\mathrm{F}$ - centres. They impart yellow colour to the crystal because they absorb energy from the visible light and get excited.
Question 27.
Classify each of the following solids as ionic, metallic, molecular, network (covalent) or amorphous.

Answer:
1. Tetra phosphorous decoxide $\left(\mathrm{P}_4 \mathrm{O}_{10}\right)$
2. Ammonium Phosphate $\left(\mathrm{NH}_4\right)_3 \mathrm{PO}_4$
3. SIC
4. $\mathrm{I}_2$
5. $\mathrm{P}_4$
6. Plastic
7. Graphite
8. Brass
9. $\mathrm{Rb}$
10. $\mathrm{LiBr}$
11. $\mathrm{Si}$

Answer:
1. Tetra phosphorous decoxide $\left(\mathrm{P}_4 \mathrm{O}_{10}\right)=$ Molecular solid
2. Ammonium Phosphate $\left(\mathrm{NH}_4\right)_3 \mathrm{PO}_4=$ Ionic solid
3. $\mathrm{SiC}=$ Covalent solid
4. $\mathrm{I}_2=$ Molecular solid
5. $\mathrm{P}_4=$ Molecular solid
6. Plastic Amorphous solid
7. Graphite $=$ Covalent solid
8. Brass $=$ Metallic solid
9. $\mathrm{Rb}=$ Metallic solid
10. $\mathrm{LiBr}=$ Ionic solid
11. $\mathrm{Si}=$ Covalent solid
Question 28.
What is the formula of a compound in which the element $\mathrm{Y}$ forms ccp Lattice and atoms of $\mathrm{X}$ occupy 2/3rd of
tetrahedral voids?
Answer:
Number of element $Y=n$, Number of element $X=2 \mathrm{nx} \frac{2}{3}$. As number of tetrahedral void $=2 n$ $\mathrm{X}: \mathrm{Y}=\frac{4 n}{3}: \mathrm{n}$
Formula $=\mathrm{X}_4 \mathrm{Y}_3$
Question 29.
The energy required to vapourise one mole of copper is smaller than that of energy required to vapourise I mol of diamond. Why?
Answer:
Copper is a metallic solid having metal-metal bonds while diamond is a covalent solid having covalent bonds.Metallic bonds are weaker than covalent bonds and thus less amount of energy is required to break metallic bonds than covalent bonds.
Question 30.
Assign reason for the following:
1. phosphorous doped silicon is a semiconductor.
2. Schottky defect lowers the density of a solid.
Answer:
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.

3 Mark Questions and Answers
Question 1.
Distinguish between isotropy and anisotropy?
Answer:
Isotropy:
1. Isotropy means uniformity in all directions.
2. Isotropy means having identical values of physical properties such as refractive index, electrical conductance in all directions.
3. Isotropy is the property of amorphous solids.
Anisotropy:
1. Anisotropy means non-uniformity in all directions.
2. Anisotropy is the property which depends on the direction of measurement. They show different values of physical properties when measured along different directions.
3. Anisotropy is the properly of crystalline solids.
Question 2 .
What are polar molecular solids? Give example.
Answer:
1. The constituents are molecules formed by polar covalent bonds.
2. They are held together by relatively strong dipole-dipole interactions.
3. They have higher melting points than the non-polar molecular solids. Eg., Solid $\mathrm{CO}_2$, Solid $\mathrm{NH}_3$.
Question 3.
Write a note about metallic solids.
Answer:
1. In metallic solids, the lattice points are occupied by positive metal ions and a cloud of electrons pervades the space.
2. They are hard and have high melting point.
3. Metallic solids possess excellent electrical and thermal conductivity. They possess bright lustre.
4. Examples - Metals and metal alloys $\mathrm{Cu}, \mathrm{Fe}, \mathrm{Zn}, \mathrm{Ag}, \mathrm{Ay}, \mathrm{Cu}-\mathrm{Zn}$ etc.
Question 4.
What are characteristic parameters of a unit cell?
Answer:
1. A basic repeating structural unit of a crystalline solid is called a unit cell.

2. A unit cell is characterised by the three edge lengths or lattice constants $a, b$ and $\mathrm{c}$ and the angle between the edges $a, P$ and $y$.
3. 

Question 5.
What are type of unit cells? Give their names.
Answer:
1. There are two types of unit cells, a) primitive b) Non - primitive.
2. A unit cell that contains only one lattice point is called a primitive unit cell, which is made up from the lattice points at each of the comers.
3. In the case of non-primitive unit cells, there are additional lattice points, either on a face of the unit cell or with in the unit cell.
Question 6.
Draw the seven types of primitive crystal systems.

Answer:

Question 7.
Draw the types of cubic crystal systems.
Answer:

Question 8.
Draw the types of orthorhombic cubic crystal systems.

Answer:

Question 9.
Calculate the number of atoms belong to one unit cell of simple cubic unit cell(sc).
Answer:
1. In the simple cubic unit cell, each corner is occupied by an identical atoms (or) ions (or) molecules and they touch along the edges of cube, do not touch diagonally. The coordination number of each atom is 6 .
2. Each atom in the comer of the cubic unit cell is shared by 8 neighbouring unit cells and therefore atoms per unit cell is equal to $\frac{N_c}{8}$. where $\mathrm{Nc}$ is the number of atoms at the corners.
3. no of atoms in a Sc unit cell $=\left(\frac{N_c}{8}\right)=\left(\frac{8}{8}\right)=1$

Question 10 .
Calculate the number of atoms per unit cell of bec type.
Answer:
1. In a body centered cubic unit cell, each corner is occupied by an identical particle and in addition to that one atom occupied the body centre.
2. Those atoms which occupy the corners do not touch each other, however they all touch the one that occupies the body centre.
3. Hence each atom is surrounded by eight nearest neighbours and coordination number is 8 . An atom present at the body centre belongs to only a particular unit cell i.e., unshared by other cell.
$\therefore$ number of atoms in a bcc unit cell $=\frac{N_c}{8}+\frac{N_b}{1}+\frac{8}{8}=\frac{1}{1}=1+1=2$

Question 11.
How will derive the formula of density of a unit cell?
Answer:
1. Using the edge length of a unit cell, we can calculate the density ( $p$ )of the crystal by considering a cubic unit cell as follows.
Density of the unit cell $\rho=\frac{\text { Mass of the unit cell }}{\text { Volume of the unit cell }}$
Mass of the unit cell $=\left\{\begin{array}{c}\text { Total number of atoms belong } \\ \text { to that unit cell }\end{array}\right\} \times$ mass of one atom
$\begin{aligned} \text { Mass of one atom } & =\frac{\text { Mo }}{\mathrm{Avagag}} \\ \mathrm{m} & =\frac{\mathrm{M}}{\mathrm{N}_{\mathrm{A}}}\end{aligned}$
Substitute the value (3) in (2)
Mass of the unit cell $=\mathrm{n} \times \frac{M}{N_A}$
For a cubic unit cell, all the edge lengths are equal. i.e., $\mathrm{a}=\mathrm{b}=\mathrm{c}$
Volume of the unit cell $=\mathrm{a} \times \mathrm{a} \times \mathrm{a}=\mathrm{a}^3$
$\therefore$ Density of the unit cell $=\rho=\frac{n M}{a^3 N_A}$
Question 12 .
Calculate the packing fraction of siniple cubic arrangement
Answer:
In a simple cubic arrangement

Packing fraction (or) efficiency $=\frac{\text { Total volume occupied by spheres in unit cell }}{\text { volume of the unit cell }} \times 100$
Consider the cube with an edge length ' $a$ '
Volume of the cube with edge length $a$ is $=a \times a \times a=a^3$
Let ' $r$ ' is the radius of the sphere
From the figure $\mathrm{a}=2 \mathrm{r} \Rightarrow \mathrm{r}=\frac{a}{2}$
$\therefore$ volume of the sphere with radius $r=\frac{4}{3} \pi r^3$
$
\begin{aligned}
& =\frac{4}{3} \pi\left(\frac{a}{2}\right)^3 \\
& =\frac{4}{3} \pi\left(\frac{a^3}{8}\right) \\
& =\frac{\pi a^3}{6}
\end{aligned}
$

In a simple cubic arrangement. number of spheres belongs to a unit cell equal to one.
$\therefore$ Total volume occupied by the spheres in sc unit cell $=1 \mathrm{x}\left(\frac{\pi a^3}{6}\right)$
Dividing 3 by 1
Packing fraction $=\left(\frac{\frac{\pi a^3}{6}}{a^3}\right) \times 100=\frac{100 \pi}{6}=52.31 \%$ Only $52.31 \%$ of the available volume is occupied by the spheres in simple cubic packing, making in efficient use of available space and hence minimizing the attractive forces.
Question 13.
What is meant by packing efficiency? How is jt measured?
Answer:
1. There is some free space between the spheres of a single layer and the spheres of successive layers.
2. The percentage of total volume occupied by these constituent spheres gives the packing efficiency of an arrangement. For eg., in simple cubic arrangement.
Packing fraction (or) efficiency $=\frac{\text { Total volume occupied by spheres in unit cell }}{\text {volume of the unit cell }} \times 100$
Question 14.
Calculate the packing efficiency in fcc unit cell?
Answer:
Total number of spheres belongs to a single fcc unit cell is 4 . Volume of the sphere with radius $r$ is $=\frac{n}{2} \pi$ $\left(\frac{\sqrt{2} a}{4}\right)^3$
$\therefore$ Volume of all spheres in fcc unit cell $=4 \times\left(\frac{\sqrt{2} \pi a^3}{24}\right)$
$
\begin{aligned}
\text { Packing efficiency } & =\frac{\left(\frac{\sqrt{2} \pi a^3}{6}\right)^3 \times 100}{a^3} \\
& =\frac{\sqrt{2} \pi}{6} \times 100 \\
& =\frac{1.414 \times 3.14 \times 100}{6}=74 \%
\end{aligned}
$
Question 15.
How is radius ratio is useful in determination of structure of an Ionic compound?
Answer:
1. The structure of an ionic compound depends upon the stoichiometry and the size of the ions.
2. Generally in ionic crystals, the bigger anions are present in the close packed arrangements the cations occupy the voids.
3. The ratio of radius of cation and anion plays an important role in determining the structure.
4. For Eg;

Question 16.
What Is meant by impurity defect? Explain with example?
Answer:
1. A method of introducing defects in ionic solids by adding impurity ions.
2. If the impurity ions are in different valence state from that of host, vaccancies are creited in the crystal lattice of the host.
3. For cg., addition of $\mathrm{CdCl}^2$ to silver chloride yields solid solutions where the divalent cation $\mathrm{Cd}^{2+}$ occupies the position of $\mathrm{Ag}^{2+}$
4. This will disturb the electrical neutrality of the crystal. In order to maintain the same, proportional number of Ag ions leave the lattice. This produces a cation vaccancy in the lattice, such kind of crystal defects are called impurity defects.
Question 17.
A compound is formed by two elements $\mathrm{M}$ and $\mathrm{N}$. The element $\mathrm{N}$ forms ccp and atoms of $\mathrm{M}$ occupy $1 / 3$ rd of the tetrahedral voids. What is the formula of the compound?
Answer:
Suppose the atoms $\mathrm{N}$ in the $\mathrm{ccp}=\mathrm{n}$
$\therefore$ No. of tetrahedral voids $=2 \mathrm{n}$
As $1 / 3 \mathrm{rd}$ of the tetrahedral voids are occupied by atoms $M$, therefore,
No. of atoms $\mathrm{M}=\frac{2 n}{3}$
$\therefore$ Ratio of $\mathrm{M}: \mathrm{N}=\frac{2 n}{3}: \mathrm{n}=2: 3$
Hence, the formula is $\mathrm{M}_2 \mathrm{~N}_3$
Question 18 .
How many lattice points are there in one unit cell of each of the following lattice?
1. Face - centred cubic
2. Face - centred tetragonal
3. Body - centered
Answer:
1. Lattice points in face-centred cubic lattice $=8$ (at corners) +6 (at the face centre) $=14$
2. Face centred tetragonal $=8$ (at corners) +6 (at the face centre) $=14$
3. Lattice points in body-centred cube $=8$ (at corners) +1 (at the body centre) $=9$
Question 19.
Explain:
1. The basis of similarities and differences between metallic and ionic crystals.
2. Ionic solids are hard and brittle.

Answer:
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. in 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.
Question 20.
$\mathrm{ZnO}$ is colourless at room temperature, while yellow when hot, why?
Answer:
$\mathrm{ZnO}$ is colourless at room temperature. When it is heated, it becomes yellow in colour. On heating, it loses oxygen and thereby forming free $\mathrm{Zn}^{2+}$ ions. The excess $\mathrm{Zn}^{2+}$ ions move to interstitial sites and the electrons also occupy the interstitial positions.
5 Mark Questions and Answers
Question 1.
What are general characteristics of solids?
Answer:
1. Solids have definite volume and shape.
2. Solids are rigid and incompressible.
3. Solids have strong cohesive forces.
4. Solids have short interatomic, ionic (or) molecular distances.
5. Their constituents (atoms, ions or molecules) have fixed positions and can only oscillate about their mean positions.
6. Unlike gases, in solids, the atoms, ions (or) molecules are held together by strong force of attraction.
Question 2.
Write a note about classification of solids with suitable examples.

Question 3.
What are ionic solids? Give their characteristics.
Answer:
1. The structural units of an ionic crystals are cations and anions. They are bound together by strong Na electrostatic attractive forces.
2. To maximize the attractive force, cations are surrounded by as many anions as possible and vice versa.
3. Ionic crystals possess definite crystals structure.
4. Many solids are cubic close packed.
Characteristics
1. Ionic solids have high melting points.
2. These solids do not conduct electricity, because the ions are fixed in their lattice positions.
3. They do not conduct electricity in molten state (or) when dissolved in water, because the ions are free to move in the molten state or solution.
4. They are hard as only strong external force can change the relative positions of ions.
5. Example - The arrangement of $\mathrm{Na}$ and $\mathrm{Cl}$ ions in $\mathrm{NaCI}$ crystal.

Question 4.
What are molecular solids?Explain their classification with suitable examples.
Answer:
In molecular solids, the constituents are neutral molecules. They are held together by weak vander Waals forces. Generally molecular solids are soft and they do not conduct electricity. These molecular solids are further classified into three types.
1. Non polar molecular solids.
2. Polar molecular solids.
3. Hydrogen bonded molecular solids.
1. Non polar molecular solids
- In this type, molecules are held together by weak dispersion forces or London forces.
- They have low melting points and are usually in liquids or gaseous state at room temperature. Examples Naphthalene, Anthracene etc.
2. Polar molecular solids
- In this type, molecules formed by polar covalent bonds.
- They are held together by strong dipole-dipole interactions.
- They have higher melting points than the non - polar molecular solids. Examples., solid $\mathrm{CO}_2$, solid $\mathrm{NH}_3$
3. Hydrogen bonded molecular solids
- The constituents are held together by hydrogen bonds.
- The constituents are held together by hydrogen bonds.
- They are soft solids under room temperature Examples: Solid ice, glucose, urea.
Question 5.
An element crystallizes in a fcc lattice with cell edge of $400 \mathrm{pm}$. The density of the element is $7 \mathrm{~g} / \mathrm{cm}^3$. How
many atoms one present in $280 \mathrm{~g}$ of the element?
Answer:
Volume of unit cell $\mathrm{a}^3(\mathrm{a}=$ edge length)
$=400 \mathrm{pm}$
$=\left(400 \times 10^{-12} \mathrm{~m}\right)^3$
$=\left(400 \times 100^{-10} \mathrm{~cm}\right)^3=64 \times 10^{-24} \mathrm{~cm}^3$
Volume of $208 \mathrm{~g}$ of the element $=\frac{208}{7 \mathrm{~g} / \mathrm{cm}^3}=29.71 \mathrm{~cm}^3$

$
\begin{aligned}
\text { Number of unit cells in this volume } & =\frac{\text { vol.of given amount }}{\text { vol of one unit cell }} \\
& =\frac{29.71}{64 \times 10^{-24}}=0.46 \times 10^{24}
\end{aligned}
$
Since each f.c.c. unit cell contains 4 atoms therefore,
Total number $=4 \times 0.46 \times 1024$, $=1.84 \times 1024$ atoms.
Common Errors
1. sc, bcc, fee structures may get confused if they ask in different order.
2. Calculation of atoms at each cube may get confused.
3. Sharing of atoms may get $\operatorname{con} \neg$ fused.
Rectifications
1. In sc, only simple cube can be drawn, bcc structure is with one dot at centre, fee structure is with sc with six dots at each face.
$s c$ - only one atom, bcc - two atoms, fee - four atoms (we can remember as $f$ and $f$ ).
2. Atom at comer is shard by 8 unit cells. Atom at centre is not shared. Atom at face is shared by 2 unit cells. Atom at edge is shared by 4 unit cells.