The Solid State Class 12 Notes CBSE Chemistry Chapter 1 (Free PDF Download)

Section – A (1 Mark Questions)

1. What type of forces hold molecules of camphor together and what solid is it?

Ans. Van der Waals forces hold camphor molecules together and this is a molecular solid.

2. LiCl acquires pink colour when heated in Li vapours. Why?

Ans. Cl- ions diffuse to surface and form LiCl with oxidized vapours of Li and an electron is released which diffuses into the crystal and occupies vacant anionic site which is called F-centres or colour centre. These F-centres are responsible for pink colour.

3. What is the coordination number of an atom in hcp?

Ans. Its C.N. is 12

4. Write a feature which distinguishes a metallic solid from an ionic solid.

Ans. Constituents forming ionic solids are three-dimensional arrangement of cations and anions while kernels and mobile sea of electrons form metallic solids.

5. Crystalline solids are anisotropic in nature. What does this statement mean?

Ans. Many physical properties like refractive index, electrical resistance etc. are different in different directions of crystalline solids which is called anisotropy.

 

6. What is the effect of Schottky defect on the density of solid?

Ans. Density of solid decreases as there is loss of matter.

7. How do metallic and ionic substances differ in conducting electricity?

Ans. Metallic substances conduct electricity through electrons while ionic substances conduct electricity in molten state or in solution through ions.

8. What is the relationship between the edge length (a) of the unit cell and radius (r) of an atom in a face centred unit cell?

Ans. $r=\frac{a}{2\sqrt{2}}$

9. Name the non-stoichiometric point defect responsible for colour in alkali metal halides.

Ans. Metal excess non-stoichiometric point defects.

10. In a close packing of N spheres, how many

(i) tetrahedral, and (ii) octahedral sites are present?

Ans. (i) Tetrahedral = 2N, (ii) Octahedral=N.

Solid State Notes PDF  - Section – B (2 Marks Questions)

11. Calculate the packing efficiency of a metal crystal for a simple cubic lattice.

Ans. Let each side of a cube is ‘a’ and radius of each particle is ‘r’ then a = 2r

The number of effective particles per unit cell is $=8\times\frac{1}{8}=1$ 

$PE=\dfrac{Volume\;occupied\;by\;lattice\;points}{Total\;volume\;of\;a\;cubic\;cell\;unit}$

$PE=\dfrac{\dfrac{4}{3}\pi r^{3}}{a^{3}or\left ( 2r \right )^{3}}=\dfrac{\pi }{6}=0.524$ 

$\therefore$  Percentage PE = 52.4%

12. Define the following terms in relation to crystalline solids.

(i) Unit Cell

(ii) Coordination Number

Ans. (i) Unit cell: It is the smallest portion of a crystal lattice, which when repeated in different directions, generates the entries lattice.

(ii) Coordination number: Number of atoms to which a particular atom is linked in a crystal lattice in a solid is called coordination number.

13. How would you determine the atomic mass of an unknown metal if you know its mass density and dimensions of the unit cell of its crystal?

Ans. $Density=\dfrac{Mass\;of\;unit\;cell}{Volume\;of\;unit\;cell}$  

Mass of unit cell $=\dfrac{Z\times M}{N_{A}}gram $

$\therefore \rho =\dfrac{Z\times M}{N_{A\times\;a^{3}}}$ a = Edge length in cm

 

14. What is a semiconductor? Describe two main types of impure semiconductors.

Ans. Solids having conductivity ranging 10-6 to $10^{4}ohm^{-1}m^{-1}$ are semiconductors. 

Semiconductors are of two types.

(a) n-type semiconductor: When elements of group-14 (i.e., Si and Ge) are doped with an element of group-15 (i.e., As and P) n-type semiconductor is obtained. The 5th valence electron in As or P is freely available for their conductance. 

(b) p-type semiconductor: When elements of group-14 (i.e., Si & Ge) are doped with elements of group-13(i.e., B and Al or Ga) etc. causes p-type semiconductors. In them an electron deficient point or hole is responsible for conductance.

15. Sodium crystallizes in a bcc unit cell. Calculate the approximate number of unit cells in 9.2 g of sodium. $(M_{Na}\;=\;23u)$ 

Ans. $n_{Na}=\dfrac{9.2}{23}=0.4$

Number of atoms of 

Na = $0.4\times 6.002\times 10^{23}=2.4088\times 10^{23}$

One BCC unit cell contains = 2 atoms

Number of unit cells in 9.2 g Na

  $= \dfrac{2.4088\times 10^{23}}{2}$

$= 1.2044\times 10^{23}$

16. KF has ccp structure. Calculate the radius of the atom if the side of the cube is 400 pm. How many F- ions and octahedral voids are there in this unit cell?

Ans. For ccp lattice, $r=\dfrac{\sqrt{2a}}{4}$ 

          $r=\dfrac{1.414\times400}{4}= 141.4\;pm$

There are $4F^{-}$ ions and four octahedral voids 

17. Three elements A, B and C crystallize into a cubic solid lattice. Atoms A occupy the corners, B occupy the cube centres and C occupy the edges centre. What is the formula of the compound?

Ans. Element A occupying corners = 1           

Effective Number of A per unit cell $=8\times\frac{1}{8}=1$  

Element B occupying body centres = 1 

Effective Number of B per unit cell = $1\times1=1$

  Element C occupying edge centres = 3

Effective Number of C per unit cell $=12\times\dfrac{1}{4}=3$ 

$\therefore$ Formula of compound $=ABC_{3}$

18. The density of lead is 11.35 g/cm3 and metal crystallizes with fcc unit cell. Estimate the radius of lead atom.

$(Pb=207, N_{A}=6.02\times10^{23}mol^{-1})$

Ans. $\rho =\dfrac{ZM}{a^{3}N_{A}} $

$a^{3}=\dfrac{ZM}{\rho N_{A}} $

$a^{3}=\dfrac{4\times207}{11.35\times6.02\times10^{23}}$

         $\therefore a=4.948\times10^{-8}$

For fcc, $r=\dfrac{\sqrt{2a}}{4}=\dfrac{1.414\times4.95\times10^{-8}}{4}$  

$r= 1.75\times10^{-8}$ cm or 175 pm

19. Tungsten crystallizes in a body-centred cubic lattice. Calculate the number of unit cells in 1.5 g of tungsten (W= 184 u).

Ans. For BCC, Z = 2

          $n_{w}=\dfrac{W}{A}=\frac{1.5}{184}$

Number of unit cells $=\dfrac{1.5\times6.02\times10^{23}}{184\times2}$  

$=2.45\times10^{21}$

20. The two ions A+ and B– have radii 88 and 200 pm respectively. In the close packed crystal of compound AB, predict the coordination number of A+.

Ans. $\frac{r_{A}}{r_{B}}=\frac{88}{200}=0.44$

Since the radius ratio lies between 0.414 to 0.732, the coordination number of A+ is 6.

Chemistry Chapter 1 Solid State Notes PDF Summary

Introduction

Apart from liquid and gaseous states, solid state is a state of matter. Solids have very strong intermolecular interactions, and there are very few vacant spaces between the atoms/ions/molecules. As a result, they have a predetermined shape and volume.

Characteristic Properties of Solids

The following properties come under the category of solids:

• Solids have high density.

• Solids have low compressibility.

• Solids are rigid in nature.

• Solids have definite shape and volume.

Classification of Solids

On the basis of the following parameter, solids are broadly classified as:

• Classification based on various properties.

• Classification based on bonding present in building blocks.

On the Basis of Various Properties

On the basis of the various properties of solids, they can be classified as:

• Crystalline solids

• Amorphous solids

Amorphous solids have an uneven structure over long distances and lack sharp properties, whereas crystalline solids have a regular structure throughout the entire volume and sharp qualities. The table below shows the many differences.

Based on Bonding

Solids are classified according to the sort of bonding present in their building units. The table below lists many types of solids as well as their properties. 

The Different Properties of the Four Types of Solids are Listed as:

Structure of Crystalline Solids

Crystal Lattice and Unit Cell

The crystalline solid regular array of building pieces (atoms/ions/molecules) is known as the "Crystal Lattice."

"Unit Cell" refers to the smallest component of a crystal lattice that can be repeated in all directions to form the full crystal lattice.

Small spheres represent the atoms of ions or molecules in a unit cell. Variations in the following parameters produce several lattices:

• The edge along the 3 axis – a, b, c.

• The interfacial angle - \[{{\alpha , \beta , \gamma }}\] 

• Location of atoms/ions with respect to each other in crystal lattice.

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Primitive Unit Cells and Bravais Lattices

There are seven different types of unit cells, as well as various subtypes of unit cells. Primitive Unit Cells or Crystal Habits are the names given to these seven unit cells. The following are listed in the table below:

For these 7 types of unit cells, 14 types of Lattices exist in nature. These 14 lattices are named as “Bravais Lattices”.

The focus will primarily be on cubic unit cells and their arrangements.

Cubic Unit Cells

The most common unit cell is this one. The atoms or spheres in a cubic unit cell can be found at the following locations.

• Corners

• Body centre

• Face centres

The contributions of a sphere stored at various locations are as follows:

Types of Cubic Unit Cells

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The following factors distinguish these unit cells from one another:

• The positions of the spheres within the unit cell.

• The unit cell's rank (effective number of spheres inside a unit cell).

• The relationship between the radius and the edge length of a single sphere.

• Fractional packing (fraction of volume occupied by spheres in a unit cell).

The following parameters are provided in the table below for all three unit cells:

Calculations Involving Unit Cell Dimensions: Density of Cubic Crystals

Unit cell is a three-dimensional structure that has one or more than one atom. The density of cubic crystals can be determined using the below-given formulas. 

If there are z number of atoms in the unit cell and m is the mass of each atom, then

Mass of a unit cell = Number of atoms in unit cell × Mass of each atom 

Mass of a unit cell = z × m

Mass of an atom can be given with the help of Avogadro number and molar mass as:

m = M/NA

where M = molar mass and NA = Avogadro’s number

Also, we know that the volume of the unit cell, V = a3

Therefore, Density of unit cell = mass of unit cell/ volume of the unit cell

Density of unit cell = z × mV =z × ma3 =z ×M a3  × NA.

Close Packing in Solids: Origin of Unit Cells

Assume we have a set of spheres of identical size that we must arrange in a single layer with the requirement that the spheres be in close proximity to one another. There are two sorts of layers that can be used:

• Square Packing

• Hexagonal Packing

Spheres are arranged in square packing in such a way that the rows are both horizontal and vertical. The Co-ordination number is 4 in this situation.

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It is more efficient to pack hexagonally. It has a Coordination number of 6 and has fewer voids than square packing. 

If we add another layer to the square packing, we can do the following:

• A comparable layer is placed just above the foundation layer, with the second layer's spheres appearing just above the first layer's spheres, and the layers are repeated. If the first layer is designated as A, the packing is of the type AA, and the unit cell is simple cubic.

• On the other hand, we get BCC unit cells and ABAB type of packing when spheres from the second layer are inserted in depressions from the first layer.

The following are examples of hexagonal foundation layer arrangements:

When we place the second hexagonal layer A in the depressions of the first hexagonal layer A, we get two sorts of voids. Hollow and through voids of layer A and layer B are the X kind of voids. Layer B voids that are directly above spheres in layer A are referred to as Y type voids. When the spheres of the second layer are placed over Y voids, layer 1 is repeated, and ABABAB type packing is obtained. The hexagonal unit cell is obtained in this arrangement, and the packing is known as hexagonal close packing (HCP). This packing has a 74 percent efficiency.

When the third layer is applied to X-type voids, a new layer C is created, and the process is repeated. Packing of the ABCABCABC type will be obtained. The FCC unit cell is used in this design, and the packing efficiency is 74%.

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Voids

Definition

Voids are the empty spaces inside a sphere. The amount and shape of voids is determined by the unit cell and packing used.

Radius Ratio

The radius ratio of a sphere that can be perfectly fit in the void to the radius of surrounding spheres is used to determine the size of the void. This is written as:

Radius ratio = \[\dfrac{{\text{r}}}{{\text{R}}}\] 

Types of Voids

Trigonal Void

It is the void formed of equal radii which touches each other as shown in the figure.

Tetrahedral Void

It is formed by the contact of four spheres and is located in the centre of a tetrahedron formed by the contact of four spheres.

Octahedral Void

Cubic Void

The voids formed by the close contact of eight spheres.

The following are the key points:

• Radius ratio is equal to $\dfrac{{\text{r}}}{{\text{R}}} = 0.732$ 

• Number of voids in a cubic crystal is 1.

• Position is at the body centre.

• Coordination number is 8.

• Rank 1.

It is clear from the above details that:

Trigonal < Tetrahedral < Octahedral < Cubic

Classification of Ionic Structures

The simultaneous arrangement of cations and anions in a lattice/unit cell produces ionic compounds. The larger of two species takes up major places in a unit cell, while the lesser species takes up vacancies in proportion to their size. Which is determined by the radius ratio. Below is a list of the various ratios.

On the basis of these ratio ranges, the ionic crystal is classified into five categories which are as follows:

${\text{NaCl}}$ Type Structure

${\text{ZnS}}$ Type Structure

Fluorite Type Structure

Anti Fluorite Structure

${\text{CsCl}}$ Type Structure

Imperfections in Solids

At 0 K, crystals are generally in perfectly ordered order. And, as the temperature increases, the electrons start moving, and cause imperfections in solids. It is called defects.

Generally, these defects or imperfections are of two types:

1. Electronic imperfections

2. Atomic imperfections (Point defects)

Electronic Imperfection in Solids

• Electrons are in lowest energy levels at absolute 0 K, and as the temperature increases electrons jump to upper or higher energy levels. 

• It creates holes in the lattice, and that causes Electronic Imperfection in Solids. 

• In general, the number of holes and electrons are equal in a lattice.

Atomic Imperfections (Point defects)

• It is caused due to improper or irregular arrangements of atoms or ions. 

• So, the defects which are caused by misplaced or missing atoms are point defects.

Types of Point Defects 

Points defects can be categorised as follows:

1. Stoichiometric point defects

1. Schottky defects

2. Interstitial defects

3. Frenkel defects

2. Non-stoichiometric point defects

1. Metal excess defects due to anion vacancies

2. Metal excess defects due to interstitial cations

3. Metal deficiency due to cation vacancies

1. Stoichiometric Point Defects: 

The stoichiometry of solids are not disturbed by these defects.The ratio of positive ions and negative ions is called stoichiometry of solids.

a. Schottky Defects: In ionic solids, it is a vacancy defect. Electrical neutrality is maintained because the number of missing cations and anions is equal. The density of the substance is reduced as a result of this flaw. Ionic compounds with almost identical cation and anion sizes demonstrate the flaw. Examples are: KCl, NaCl, AgBr.

b. Interstitial Defect: Ions or atoms occupy vacant interstitial sites and cause interstitial defects. Interstitial sites are the sites located between regular positions and are empty.

c. Frenkel Defect: When an ion leaves its existing/correct lattice site and occupies an interstitial site, it causes frenkel defect. It mostly occurs in the compounds having a large size difference between the positive and negative ions. Examples are: ZnS, AgCl, AgI.

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2. Non-stoichiometric Point Defects

The defects which make changes to the stoichiometry of the compounds are called 2. Non-stoichiometric point defects.

Non-stoichiometric or Berthollide compounds are those in which the ratio of positive and negative charges of ions is different from the ideal chemical formula of the compounds.

a. Metal Excess Defects due to Anion Vacancies: These defects generally found in the crystals possess Schottky defects. In it, the negative ion leaves its lattice site and generates a hole which could occupy the negative ion, i.e., the electron. 

F-centres are those holes occupied by the negative ion, i.e., electron.

b. Metal Excess Defects due to Interstitial Cations: These defects generally found in the crystals possess Frenkel defects. In it, an extra positive ion or hole is present in an interstitial site. An extra electron neutralises a positive ion.

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c. Metal Deficiency due to Cation Vacancies: These are the defects caused due to the absence of a metal ion from its actual lattice site.

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Properties of Solids: Electrical Properties and Magnetic Properties

Electrical Properties of Solids

Solids can be classified into three types based on their electrical properties.

1. Conductors or metals

2. Semiconductor

3. Insulator

Range of Electrical Conductivity of Solids

Effect of Temperature on Electrical Conductivity

Reason of Conductivity in Solids

Magnetic Properties of Solids

Solids can be classified into five types based on their behaviour towards magnetic fields.

1. Diamagnetic substances

2. Paramagnetic substances

3. Ferromagnetic substances

4. Anti-ferromagnetism substances

5. Ferrimagnetism substances

Difference between Diamagnetic, Paramagnetic, Ferromagnetic, Anti-ferromagnetism and Ferrimagnetism substances

Revision Notes of Chemistry Class 12 Chapter 1- The Solid State

Notes of Chemistry Class 12 Chapter 1

Class 12 Chapter 1 Chemistry The Solid State introduces students to the basic concept of Solids, their types and characteristics. To understand all the essential concepts covered in Chemistry Chapter 1, students first understand what is meant by solids. The definition of Solids, along with its types and other crucial concepts related to it are covered in the well-explained and straightforward way in Class 12th Chemistry Chapter 1 notes.

Solids: Such chemical substances which have definite size, shape, volume and rigidity are known as Solid substances. These substances have high density and low compressibility.

There Are Two Types of Solids

• Amorphous Solids

• Crystalline Solids

Other Crucial Concepts Covered Under Class 12 Chemistry Ch 1 Notes:

• Classification of Solids

• Structure of Crystalline Solids

• Different types of Solids

• Square Packing 

• Hexagonal Packing 

• Types of Cubic Unit Cells 

• Voids

• Types of Voids

• Trigonal Voids

• Octahedral Voids

• Cubic Voids

• Ionic Structure 

• Fluorite Structure 

• Metal Excess Defect

• Metal Deficiency Effect

Some Important Questions of Chapter 1 Chemistry Class 12 

1. Define the term 'amorphous'. Give a few examples of amorphous solids.

2. What makes a glass different from a solid such as quartz? Under what conditions could quartz be converted into glass?

3. How many e lattice points are there in one unit sale of each of the following lattices? 

• Face centred cubic

• Face centred tetragonal

• Body-centred

4. Define the structure of crystalline solids.

5. Define the types of cubic unit cells.

6. Classify the ionic structures.

7. Explain the metal deficiency defect

Benefits of Using Class 12 Chemistry Chapter 1 Revision Notes

To make learning fun and easy for students, Class 12 Chemistry Chapter 1 notes are available in PDF file to download for free from the official website of Vedantu and its app. After downloading, students can access these notes offline as well for the quick revision of essential terms and concepts.

CBSE Class 12 Chemistry Chapter 1 notes will help the students in practising the questions that are going to be asked in their examinations. These notes will help them score better in their board examinations.

Important Topics for Solid State Class 12 Notes PDF

Explore the essential topics covered in Class 12 Solid State notes through the curated list of important topics. These notes delve into the fundamental concepts of solid-state physics, providing comprehensive coverage of key areas essential for a thorough understanding of the subject. Whether you're reviewing for exams or seeking a deeper comprehension of solid-state principles, these list of links serve as a valuable resource to aid in your Solid State Class 12 Notes PDF.

• Amorphous Solid

• Difference Between Crystalline and Amorphous Solid

• Classification of Crystalline Solids

• Crystal Lattices and Unit Cell

• Unit Cell Packing Efficiency

• Imperfections or Defects in a Solid

Important Chapter Wise Related Links

Conclusion

Notes of Chapter 1 Chemistry Class 12 will help the students in grasping the contents very quickly in an easy to understand language. These notes are made by subject experts and provide very detailed information about every crucial topic. You will surely be able to ace in your examination if you study CBSE Class 12 Chemistry Chapter 1 Notes provided by us. These notes will also help you in your other competitive exams and higher studies for reference.