Class 12 Chemistry Chapter 1 Notes – Solid State

The class 12 Chemistry chapter 1 Solid State is an important chapter that helps you understand the basics of Chemistry. It focuses on the State of Matter which forms the fundamentals for many branches later on. To perform extraordinarily in the Class 12 Chemistry board exam, students must understand Chapter 1 thoroughly. They can take help from class 12 Chemistry chapter 1 notes prepared by the expert Extramarks, who have the best knowledge of the latest CBSE syllabus and Class 12 board exam pattern.

Class 12 Chemistry Chapter 1 notes consist of a brief about Solid State and various essential questions that are highly likely to come in the board exam. These notes are convenient and reliable as they are created after analyzing previous years’ Class 12 Chemistry papers to include all the important questions and topics in an accessible language in one place.

Students may refer to chapter 1 Chemistry class 12 notes on Extramarks to prepare for their examination. 

Key Topics Covered Under Class 12 Chemistry Chapter 1 Notes 

The chapter, Solid State, includes information on the various types of solids and different forces responsible for binding the particles together, the arrangement of unit cells in lattice and packing of lattice points, and the Calculation of unit cell density and its dimension. 

It explains the Calculation of packing efficiency of solids, different types of voids, their locations and the number of voids in other arrangements. It also describes imperfections or common defects in solid states. A detailed description of Chapter 1 also includes the electrical and magnetic properties of solids which are described in Extramarks chapter 1 Chemistry class 12 notes. 

A brief of the chapter 1 Chemistry class 12 notes is as under.

Introduction

Everything that surrounds us is matter, divided into three states: solid, liquid and gas. Solids play a crucial role in pursuing different purposes in our daily lives. The elementary particles and the type of bonds between the particles determine the nature of a specific solid. For, e.g. Buckets or a container used to carry water, utensils used for cooking food, computers, vehicles, electronic gadgets, notebooks, pencils, papers etc. are all solid substances used in our day-to-day life.

The Solid is a state of matter in which the fundamental particles are organized very closely. The constituent particles can be atoms, ions or molecules.

Characteristics Properties of the Solid State

• They have definite mass, volume and shape.
• Intermolecular distances are short.
• Intermolecular forces are strong.
• Their essential particles (atoms, molecules or ions) have fixed positions and can only oscillate about their mean positions.
• They are rigid and incompressible.

Students can refer to the short notes, MCQ questions and different solutions in addition to chapter 1 Chemistry class 12 notes to understand the characteristic properties of the Solid State. 

Amorphous Solids

Amorphous solid is derived from the Greek word amorphous, meaning no form. The constituent particles are arranged in a short-range order with a regular and periodically repeating pattern over short distances. These solids get softened at a specific temperature and can be moulded and drawn into numerous desired shapes. Solids may also obtain a crystalline form at some temperature when heated. This concept is clearly explained in chapter 1 Chemistry class 12 notes.

These solids can flow very slowly, also known as pseudo solids or supercooled liquids. These solids are isotropic due to the absence of long-range order and irregular arrangement of the constituent particles in all directions. This solid leads to the same value of the physical property and all the rules. Amorphous solids examples are Glass, rubber, amorphous silicon and plastics.

Amorphous silicon is a photovoltaic material broadly used to convert sunlight into electricity. Students may refer to Class 12 Chemistry Chapter 1 to understand all the key concepts. 

 Crystalline Solids

This range of solids consists of a vast range of tiny crystals having a definite characteristic geometrical shape. The constituent particles are arranged in a long-range order (symmetry and order of constituent particles that occur again at any distance from a given atom due to the interaction between the particles) with uniform and periodically repeating patterns over the entire crystal.

Crystalline solid has a sharp melting point. Crystalline solids are anisotropic due to different arrangements of particles in different directions. This solid leads to varying physical property values and the various directions in the same crystals. All  Metallic elements, including iron, copper and silver, are important examples of crystalline solids. Instead of non–metallic elements like sulphur, phosphorus, iodine and compounds like NaCl, zinc sulphide, naphthalene and quartz are actual examples of crystalline solids. 

These solids can further be divided into four categories based on the nature of intermolecular forces acting over them. Students can refer to class 12 Chemistry chapter 1 notes to know more about crystalline solids. 

Molecular Solids

Under this section of class 12 Chemistry chapter 1 notes, students will learn that solids composed of molecules as constituent particles are molecular solids. These molecular solids can further be categorized into the following types: 

1. i) Non-Polar Molecular solids:

• They are composed of either atom.
• H2, Cl2 and I2 are a few of the primary examples.
• In non-polar Molecular solids, the atoms or molecules are grasped together by London forces or weak dispersion forces.
• They are soft and non-conductors of electricity.
• They have very low melting points and usually exist in a liquid or gaseous state at room temperature and pressure. Students can refer to detailed information on molecular solids in Class 12 Chemistry Chapter 1 notes.

1. ii) Polar Molecular Solids:

• The molecules like HCl, and SO2, are created by polar covalent bonds.
• In polar molecular solids, the constituents atoms or molecules are grasped together by stronger dipole-dipole interactions.
• Polar molecules are non-conductors of electricity and are soft.
• The melting points of these polar molecular solids are higher than those of non-polar molecular solids. They are usually obtained in a liquid or gaseous state at room temperature and pressure.
• Molecules like SO2 and solid NH3 are a few examples of polar molecular solids.

    (iii) Hydrogen-Bonded Molecular Solids:

• Hydrogen-Bonded Molecular Solids contain polar covalent bonds between Hydrogen and Fluorine, Oxygen or Nitrogen.
• Strong hydrogen bonding holds together molecules of such solids as H2O (ice).
• Generally, they are non-conductors of electricity and are volatile liquids or soft solids under room temperature and pressure. Students may refer to class 12 Chemistry chapter 1 notes.  

Ionic Solids

Under this section of class 12 Chemistry chapter 1 notes, students will learn about ionic solids. 

Ions are the constituent particles of these solids. Such solid is composed of three-dimensional arrangements of cations and anions that are bonded by strong coulombic (electrostatic) forces. These solids are hard and brittle and have high melting and boiling points. They are electrical insulators in a solid state due to the absence of movement of free electrons but are good conductors in a molten state due to ions’ activity. 

Metallic Solids

In this section of class 12 Chemistry chapter 1 notes, students get detailed information on metallic solids. In metallic solids, positive ions are surrounded by mobile free electrons and evenly spread over the crystal. Each metallic atom donates one or more electrons to the group of mobile electrons, increasing the metallic elements’ electrical and thermal conductivity. The electric field application makes these electrons flow through the linkage of positive ions. The heat applied to one metal portion makes the thermal energy spread uniformly through free electrons.

Another critical characteristic of the metal is the presence of free electrons in metals, making them lustrous, highly malleable, and ductile. For example, Cr, Fe etc., which is clearly mentioned in class 12 Chemistry chapter 1 notes. 

Covalent solids

Crystalline solids of non-metals comprise covalent bonds between adjacent atoms that are strong and directional; therefore, atoms are held very firmly at their positions all over the crystal. They are also called giant molecules, and such solids are rigid and brittle.

As defined in class 12 Chemistry chapter 1 notes, covalent solids have high melting points and decompose before melting. They are good insulators and do not conduct electricity. Silicon carbide and diamond are actual examples of such solids, but Graphite is an exception as it is a conductor of electricity and is soft.

Why is Graphite soft and a good conductor of electricity?

As defined in class 12 Chemistry chapter 1 notes, Graphite is a covalent solid that acts as a good conductor of electricity and is soft. The carbon atoms of Graphite are determined in various layers and are covalently bonded to 3 of its neighbouring atoms in the very same layer. The fourth valence electron is present between various layers and is free to move, making Graphite a good conductor of electricity. The characteristic feature of sliding between divergent layers makes Graphite a soft, excellent solid lubricant. 

Students can refer to the detailed description of Graphite in Class 12 Chemistry Chapter 1 notes. 

Crystal Lattices

In this section of class 12 Chemistry chapter 1 notes, students study crystal lattice. The main characteristic of Crystalline solids has a regular and repeating pattern of constituent particles. The diagrammatical representation of three-dimensional arrangements of constituent particles of a crystal in space with each particle depicted as a point is called a crystal lattice. There are only 14 possible three-dimensional lattices which are known as Bravais Lattices. Each point in a lattice is called a lattice site or lattice point. Each lattice point in a crystal lattice signifies one constituent particle, an atom, an ion or a molecule. Lattice points are arranged together using straight lines to identify the geometry of the lattice. 

Crystal Lattices and Unit Cells:

If each constituent particle in a crystal is depicted as a point in a three-D arrangement, this 3 D arrangement is called a Crystal lattice. The structure is an ordered array of ions, atoms or molecules. The class 12 Chemistry chapter 1 notes include more information as given under. 

Unit Cell: As we know, that unit cell is the smallest repeating unit of the crystal lattice, the building block of a crystal.

Different kinds of Unit Cells: A lattice can be created by repeating a tiny portion known as the unit cell. The different varieties of the unit cell are :

1. Primitive Cubic Unit Cell
2. Body-centred Cubic Unit Cell
3. Face centred cubic unit cell

Number of Atoms in a Unit Cell

The class 12 Chemistry chapter 1 notes give detailed information on atoms in a unit cell as under. 

1. Primitive Cubic unit Cell

The primitive unit cell has atoms only at its corner. Every atom at a corner is shared between 8 adjacent unit cells, four-unit cells in the same layer and 4-unit cells of the upper or lower layer. Hence, only 1/8th of an atom belongs to a particular unit cell.

1. Body-Centred Cubic unit Cell

The body-centred cubic unit cell has an atom at every corner and one atom at its body centre.

Number of Atoms in BCC Cell:

Thus, in a Body Centred Cubic unit cell, we have:

i)Eight corners × 1/8 per corner atom = 8 × 1/8 = 1 atom

1. ii) One  body centre atom = 1 × 1 = 1 atom

Thus, the total number of atoms present per unit cell = 2 atoms.

1. Face-Centred Cubic unit Cell

A face-centred unit cell consists of atoms at all the corners and the centre of all the faces of the cube. The atom present at the face centre is shared between two adjacent unit cells, and only half of each atom belongs to an individual unit cell. For a detailed description of unit cell students, refer to class 12 Chemistry chapter 1 notes. 

Number of Atoms in FCC Cell

1. i) 8 corners atom × 1/8 per corner atom unit cell = 8 × 1/8 = 1 atom
2. ii) Six face-centred atoms × 1/2 atom per unit cell= 6 x 1/2= 3 atoms

Thus, the total number of atoms in a unit cell = 4 atoms

Close Packed Structures

As mentioned in class 12 Chemistry chapter 1 notes, the constituent particles are close-packed in solids and leave minimum vacant space.

1. Close Packing in One Dimension

In close packing of 1 dimension, spheres are arranged in a row such that adjacent atoms are in contact with each other. Coordination no. is defined as the no. of nearest neighbour particles. In the case of one-dimensional close packing, the coordination number equals two.

1. Close packing in Two Dimensions

With reference to class 12 Chemistry chapter 1 notes, a row of closed packed spheres is assembled in two-dimensional close packing to obtain a two-dimensional pattern. This stacking is done in two different ways, Square close packing and Hexagonal close packing. (Square closed packing AAAA type and Hexagonal close-packing ABAB type)

1. Close Packing in Three Dimensions

Crystalline solids show a regular and repeating pattern of constituent particles. Three-dimensional closed packing is:

(i) The three-dimensional close packing forms two-dimensional square close-packed layers as described in class 12 Chemistry chapter 1 notes

• The second layer is arranged over the first layer so that the spheres of the upper layer are precisely above those of the first layer.
• In this arrangement of spheres, a pair of layers are precisely aligned horizontally and vertically.
• Let the first row be an ‘A’ type row, and the second row be a ‘B’ type row.
• Thus this lattice has a pattern AAAA…..
• Therefore, the lattice created is the simple cubic lattice, and its unit cell is the primitive cubic unit cell.

(ii) Three-dimensional close packing from 2-dimensional hexagonal close-packed layers.

With reference to class 12 Chemistry chapter 1 notes, a three-dimensional close-packed structure can be obtained by placing layers over each other such as putting the second layer over the first layer and the third layer over the second layer, and hexagonal closed packed layers shows an ABAB pattern. 

Placing the second layer over the first layer: 

This section of the class 12 Chemistry chapter 1 notes explains the stake of two layers of closed packed spheres and voids. Consider a two-dimensional hexagonal close-packed layer of type ‘A’ and place a similar layer above it such that the spheres of the second layer are placed in the depressions of the first layer. As the second layer is aligned differently, let it be of type ‘B’. It can be observed from the image that not all the triangular voids of the first layer are covered by the spheres of the second layer. This gives rise to another arrangement. A tetrahedral void is produced where a sphere of the second layer is above the void of the first layer area (or vice versa).

• These are tetrahedral voids because tetrahedron is formed when the centres of these four spheres are joined.
• On the other side, the triangular voids in the second layer are above the triangular voids in the first layer, and the triangular shapes of these do not overlap.
• One of them has the triangle’s apex pointing upwards and the other downwards.
• Such voids are surrounded by six spheres and are known as octahedral voids. These voids have been marked as “O” or in the form of a circle.

Introduce a number of close-packed spheres are N, so:

The number of octahedral voids created in the structure = N

The number of tetrahedral voids caused in the structure = 2N

Students can refer to NCERT Solutions for Class 12 Chemistry Chapter 1 notes to know more about voids. 

Packing efficiency:

In all types of packing, there is always some free space in the form of voids or vacant space. The overall percentage of space filled by the particle is called packing efficiency.

Packing efficiency in hcp and ccp structures: Defining packaging efficiency in class 12 Chemistry chapter 1 notes, when the unit cell edge length is ‘a’ and face diagonal AC = b.

In ABC

AC2 = b2 = BC2 + AB2

=a2 + a2 = 2a2

b= 2a

whether r is  the radius of the sphere. So we get

b= 4r=2a

a=4r/2 =22r

Each unit cell in the ccp structure has four spheres. Hence the total volume of four spheres equals 4 X (4/3)Π r3, and the cube volume is a3 or  (2√2r)3.

Hence, Packing efficiency = (Volume occupied by four spheres in the unit cell X 100)/( Total volume of the unit cell)%

= 4X (4/3))Π r3 X 100/(22r)3%

=( 16/3))Π r3 X 100/(162r)3% = 74%

Students may refer to various other study materials in addition to class 12 Chemistry chapter 1 notes to know more.

The efficiency of Packing in Body Centred Cubic Structures

In EFD,

b2 = a2 + a2 =2a2

Now in AFD

C2 = a2 + b2 = a2 + 2a2 = 3a2

c =3a 

The length of the body diagonal c = 4r, so r is the radius of the sphere as all the three spheres, along with the diagonal, touch each other. Therefore,

3a  = 4r

a = 4r3

r =34a

This type of structure has two atoms, and their volume is 2X(4/3)r3

The volume of the cube= a3=(4r3)3

So Packing efficiency = (Volume occupied by two spheres in the unit cell X 100)/( Total volume of the unit cell)

= 2X4/3 r 3 X 100/(43)r3 %

=8/3r 3 X 100/64/(33)r3 % = 68%

Students can refer to the short notes, MCQ questions, and different solutions to the Chemistry chapter 1 class 12 notes. 

Packing Efficiency in Simple Cubic Lattice

a = 2r

Here a = Edge length or side of the cube

and r = radius of a particle,

The volume of the cubic cell = a3 = (2r)3 = 8r3

A simple cubic cell contains only one atom. The volume of the occupied space is =4/3 Π r3

Packing efficiency = (Volume of one atom X 100)/( Volume of the cubic unit cell)%

= 4/3r3/8r3 X 100 = /6 X 100 = 52.4%

Thus it can be concluded that ccp and hcp structures have maximum packing efficiency.

Students can refer to the NCERT solution for class 12 Chemistry chapter 1 notes to learn about packing efficiency.

Calculations Involving Unit Cell Dimensions

Referring to class 12 Chemistry chapter 1 notes, the edge length of a unit cell dimension of a cubic crystal = a,

The density of the solid substance = d

Molar mass = M

The volume of a unit cell = a3

Mass of the unit cell = no. of atoms in unit cell × mass of each atom = no. of atoms present in one unit cell (z) × mass of a single atom (m)

m = M/NA

M is the molar mass

Therefore, the density of unit cell = m = M/NA

The density of unit cell = mass of unit cell/volume of a unit cell

zm/a3 = zM/a3NA

d = zM/a3NA

so, the density of the unit cell is the same as the density of the substances. Students may refer to various other study materials such as CBSE revision notes and CBSE question papers in addition to class 12 Chemistry chapter 1 notes.

Imperfections in Solids

Constituent particles in crystalline solids are kept in a short-range as well as long-range order, yet crystals are not perfect. Tiny crystals have irregularities in the arrangement of constituent particles when the crystallisation process occurs at a fast or moderate rate. For a detailed description of point effects, refer to NCERT books in addition to class 12 Chemistry chapter 1 notes. 

As defined in Chemistry chapter 1 class 12 notes, these defects are of two types- point and line defects. The irregularities from the ideal arrangement around a point or an atom in a crystalline substance. The irregularities or variations from an ideal position in entire rows of lattice points are called line defects. These irregularities are called crystal defects.

Imperfections or defects in crystalline solid can be categorised into four groups, namely line defects, point defects, volume defects and surface defects. Historically, crystal defects were first regarded in ionic crystals, not in metal crystals that were much simpler.

There are three types of point defects:

1. Stoichiometric defect –
   1. Frenkel defect 
   2. Schottky defect
2. Impurity defect
3. Non-Stoichiometric defect

1. Stoichiometric Defect: In this type of point defect, the ratio of positive and negative ions (Stoichiometric) and electrical neutrality of a solid are not disturbed. Sometimes it is also called intrinsic or thermodynamic defects, as mentioned in class 12 Chemistry chapter 1 notes.

They are of two types:

• Vacancy defect: When an atom disappears at its lattice sites, that is vacant, creating a vacancy defect because the density of a substance decreases.
• Interstitial defect: A defect in which an atom, ion or molecule occupies the intermolecular spaces in a crystal lattice. In this interstitial defect, the density of the substance increases.

A non-ionic compound mainly represents vacancy and interstitial defects. An ionic compound shows the same in the Frenkel and Schottky defect. Students can access the Extramarks short notes and different solutions apart from class 12 Chemistry chapter 1 notes while studying.

Stoichiometric defects can be further divided into

iii. Frenkel Defect: The smaller ion (cation) moves out of its place and occupies an intermolecular space in ionic solids. In this case, a vacancy defect is formed in its original position and the interstitial defect at its new position.

• It is also called a dislocation defect.
• The density of a substance remains unchanged.
• It happens when there is a vast difference in the size of anions and cations.

Example: ZnS, AgBr and silver chloride due to the small Ag and Zn ion size.

iv) Schottky Defect: It is a vacancy defect in ionic solids. But in ionic compounds, we require to balance the electrical neutrality of the compound so the same number of anions and cations will be missing from the compound.

•  It reduces the density of the substance.
• In this defect, the size of cations and anions are almost the same.
• Example NaCl, KCl, CsCl, and AgBr. It illustrates that AgBr shows both Frenkel and Schottky defects. 

Students can refer to the short notes, CBSE sample paper, important questions, and different solutions in addition to class 12 Chemistry chapter 1 notes to understand the concept properly.

2. Impurity Defect: Let’s understand the impurity defect by an example. If molten NaCl is crystallised with strontium chloride compound, then each Sr2+ ion replaces 2 Na+ ions and occupies the place of 1 Na+ ion. The other site remains vacant and creates an impurity defect. The solid solution of CdCl2 and AgCl is another similar example.
3. Non-Stoichiometric Defect: In this defect, the cations and anions ratio is disturbed by adding or removing ions. An example of this type is FeO which is mainly obtained with a composition of Fe0.95O.

Types of Non-Stoichiometric Defects as mentioned in class 12 Chemistry chapter 1 notes include

1. Metal deficiency defect: In this defect, the solids have a minimal number of metals compared to the Stoichiometric proportion.
2. Metal excess defect: The metal excess defect is of two types :
   1. Metal excess defect due to anionic vacancies: This occurs due to the absence of anions from its original lattice site in crystals. Thus, instead of anions, electrons occupy their position.
   2. Metal excess defect due to the presence of cations at interstitial sites: Here, on heating the compound, it releases excess cations. These additional cations occupy the interstitial sites in crystals, and the same number of electrons goes to neighbouring interstitial sites.

This section is just an overview of point defects in solids. Students may refer to NCERT solutions class 12 Chemistry chapter 1 notes for more information.

Electrical Properties

Solids can be categorised into three types based on their conductivities; Conductors, Insulators and Semiconductors.

Conduction of Electricity in Metals

• A conductor may conduct electricity due to the movement of electrons or ions.
• Metals conduct electricity equally in the solid-state and the molten state.
• The conductivity of metals depends upon the number of valence electrons available per atom.
• The atomic orbitals of metal atoms from molecular orbitals close in energy to each other and create a band.
• Partial filling or overlapping with a higher energy unoccupied conduction band allows the electrons to flow easily under an applied electric field.
• This results in the conductivity of metals.

If the space between the valence band and the conduction band is large, electrons cannot jump to it, and such a substance has minimal conductivity, making it behave as an insulator.

Conduction of Electricity in Semiconductor

Class 12 Chemistry notes discuss the conduction of electricity in semiconductors. In the case of semiconductors, the space between the valence band and conduction band is tiny. It enables some electrons to jump to the conduction band and exhibit their conductivity. The electrical conductivity of semiconductors increases with an increase in temperature since more electrons can jump to the conduction band due to the small gap between the valence band and the conduction band. Germanium and silicon show this behaviour and are known as Intrinsic semiconductors.

Doping: The conductivity of metal increases by adding an appropriate amount of suitable impurity. This process is known as doping. It can be generated with an impurity electron-rich or electron-deficient than the intrinsic semiconductor silicon or germanium. Based on the doping, Semiconductors are of 2 types –

N-type Semiconductor

• When doped with group 15 elements(P, As, Sb), Intrinsic semiconductors form n-type semiconductors.
• Si and Ge being group 14 elements have four valence electrons. They form four covalent bonds with neighbour atoms.
• Group 15 elements have five valence electrons and occupy some lattice sites.
• 4 electrons out of 5 electrons form covalent bonds.
• The remaining 1 electron is mobile and conducts electricity.
• Conductivity is due to negatively charged electrons.

P-type Semiconductor

• When doped with group 35 elements(B, Al, Ga), Intrinsic semiconductors form p-type semiconductors.
• Group13 elements have three electrons.
• Fourth, valence electrons form a hole.
• This hole moves in the reverse direction of the electric field applied, causing conductivity.
• Conductivity is due to positively charged electrons.

Applications of n-type and p-type semiconductors

Under this segment of class 12 Chemistry chapter 1 notes, students learn about the application of n-type and p-type semiconductors. 

• n-type and p-type semiconductors find great use in manufacturing electronic components.
• A diode is a mix of n-type and p-type semiconductors extensively used as a rectifier.
• Transistors are produced by keeping a layer of one semiconductor between two layers of another type of semiconductor.
• npn and pnp type of transistors detect or amplify radio or audio signals.
• The solar cell is an efficient photo-diode used to convert light energy into electrical energy.
• Gallium arsenide (GaAs) semiconductors have a speedy response and have transformed the design of semiconductor devices.
• Transition metal oxides represent marked differences in electrical properties.
• TiO, CrO2 and ReO3 behave like metals.
• Rhenium oxide, ReO3 resembles metallic copper in its conductivity and appearance.
• Certain other oxides like VO, VO2, VO3 and TiO3 show metallic or insulating properties depending on temperature.

Students can refer to NCERT Books, CBSE previous year question papers, and revision notes in addition to class 12 Chemistry chapter 1 notes to prepare for the examination. 

Magnetic Properties

Every substance possesses magnetic properties originating from the electrons present in them.

• Each electron in an atom behaves like a tiny magnet.
• The magnetic moment of these substances originates from two types of motion

 orbital motion around the nucleus and

• its spin around its axis.
• Electron, a charged particle, undergoes these motions and can be considered a small loop of current possessing a magnetic moment.
• Therefore, each electron has a permanent spin and an orbital magnetic moment.
• The magnitude of this magnetic moment is tiny and is measured in the unit called Bohr magneton, μ B, equal to 9.27 × 10–24A m2.

As mentioned in class 12 Chemistry chapter 1 notes, based on their magnetic properties, substances can be classified into five categories:

• Diamagnetic materials 

A magnetic field weakly repels diamagnetic substances. This diamagnetic property is represented by the substances in which all the electrons are paired, and there are no unpaired electrons. They are weakly magnetised on the application of magnetic fields in opposite directions. The pairing of electrons cancels out their magnetic moments, and they lose their magnetic character.

For example, H2O, NaCl and C6H6 are some examples of such substances.

• Paramagnetic materials

In this, paramagnetic substances are weakly attracted by a magnetic field. It is due to the presence of one or more unpaired electrons which are attracted by the magnetic field. The function of a magnetic field magnetises the paramagnetic substances in the same direction. They drop their magnetism in the absence of a magnetic field.

O2, Cu2+, Fe3+, and Cr3+ are some examples of such paramagnetic substances.

• Ferromagnetic materials

Ferromagnetic substances get strongly attracted to the magnetic field. They can be permanently magnetised. In solid-state, the metal ions of ferromagnetic substances are grouped into small regions known as domains that act like a tiny magnet. In an unmagnetised ferromagnetic substance, the domains are randomly oriented, cancelling their magnetic moments.

Suppose metal ions are placed in a magnetic field. In that case, all the domains of the substance are aligned in the direction of the magnetic field, forming a strong magnetic effect that persists even if the magnetic field is removed. The ferromagnetic substance forms a permanent magnet. For example, iron, cobalt, nickel, gadolinium and CrO2 are ferromagnetic substances. Whereas in the case of Antiferromagnetism, domains are oppositely oriented, thereby cancelling out each other’s magnetic moment. For example, MnO.

• Ferrimagnetism materials

Magnetic moments of the domains in the substance are aligned in parallel and antiparallel directions in unequal numbers. They are weakly attracted by magnetic fields as compared to ferromagnetic substances.

For example, Fe3O4 (magnetite) and ferrites like MgFe2O4 and ZnFe2O4. These substances also lose ferrimagnetism on heating and become paramagnetic.

While the class 12 Chemistry chapter 1 notes give a lot of study materials, it would help if students referred to CBSE revision notes and solutions.

Key Features Of NCERT Solutions for Class 12 Chemistry Chapter 1 Notes

The Chemistry Class 12 Chapter 1 notes are a vital part of a  student’s academic excellence. These study materials can help the students grasp the contents quickly in an easy to understand language. Some of the key features of class 12 Chemistry chapter 1 notes include

• These notes are made by subject experts Extramarks 
• They provide very detailed information about every critical topic. 
• Students can refer to them to study for the board exams.
• These notes can be referred to while preparing for competitive exams, IIT, JEE and more.
• They can be used for higher studies as reference materials.