Chemical Bonding as the name suggests means the interaction of different elements or compounds which defines the properties of matter.

Chemical Bonds: Definition, Types, Lewis’s Theory, Kossel’s Theory Rules, Examples

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Chemical Bonding as the name suggests means the interaction of different elements or compounds which defines the properties of matter.

Chemical bonds are formed when either at least one electron is lost to another atom, obtaining at least one electron from a different atom, or transferring one electron to another atom.

What is Chemical Bonding?

Chemical bonding is the formation of a chemical bond between two or more atoms, molecules, or ions that results in the formation of a chemical compound. These chemical bonds are what hold the atoms in the resulting compound together.

Chemical bonding is the attractive force that holds various constituents (atoms, ions, etc.) together and stabilizes them through the overall loss of energy. As a result, chemical compounds are dependent on the strength of the chemical bonds between their constituents; the stronger the bonding between the constituents, the more stable the resulting compound.

The inverse is also true: if the chemical bonding between the constituents is weak, the resulting compound will be unstable and will easily undergo another reaction to produce a more stable chemical compound (containing stronger bonds). Atoms try to lose energy in order to find stability. When one form of matter interacts with another, a force is exerted on the first. When the forces of nature are attractive, the energy decreases. When the forces of nature are repulsive, the energy increases. The chemical bond is the attractive force that holds two atoms together.

Theories on Chemical Bonding

There are two important theories on chemical bonding, and those are:

  • Lewis’s Theory of Chemical Bonding
  • Kossel’s Theory of Chemical Bonding

Let’s understand these theories in detail as follows:

Lewis Theory of Chemical Bonding

The Lewis theory of chemical bonding, also known as the Lewis electron dot theory, was proposed by the American chemist Gilbert N. Lewis in 1916. It provides a simple model to understand how atoms bond together to form molecules by focusing on the arrangement of valence electrons.

According to the Lewis theory, atoms gain, lose, or share electrons in order to achieve a stable electron configuration similar to that of noble gases. Noble gases have complete outer electron shells, making them highly stable and unreactive. Lewis recognized that other atoms tend to react in ways that allow them to acquire a similar electron configuration.

Key points of Lewis’s Theory of Chemical Bonding are as follows:

  • An atom is made up of two parts: a positively charged Kernel (the nucleus plus the inner electrons) and an outer shell that contains electrons.
  • The outmost shell can only hold a maximum of eight electrons.
  • The outer shell’s eight electrons occupy the four corners of a cube that surrounds the ‘Kernel.’
  • Atoms with an octet configuration, i.e., 8 electrons in the outermost shell, represent a stable configuration.
  • In general, an element’s valency is equal to the number of dots in the corresponding Lewis symbol or 8 minus the number of dots (or valence electrons).
  • Atoms with eight electrons in their outer shell are said to have a stable configuration. Atoms with fewer than eight electrons in their outer shell will try to gain electrons to achieve a stable configuration. Atoms with more than eight electrons in their outer shell will try to lose electrons to achieve a stable configuration.
  • Chemical bonds are formed when atoms share, gain, or lose electrons to achieve a stable configuration.
    • The number of dots in a Lewis symbol represents the number of valence electrons in an atom. 
    • The valency of an atom is the number of valence electrons that an atom can share, gain, or lose to achieve a stable configuration.

The key concept in the Lewis theory is the valence shell, which consists of the outermost energy level of an atom. Lewis represented valence electrons as dots around the atomic symbol. For example, the element oxygen (O) has six valence electrons, so it is represented as O with six dots around it.

Chemical Bonding as the name suggests means the interaction of different elements or compounds which defines the properties of matter.

Explanation of Bonds using Lewis Theory

The Lewis theory uses electron-dot symbols to depict the valence electrons of atoms and then suggests that atoms form bonds by sharing or transferring these electrons. The two main types of chemical bonds described by the Lewis theory are:

  • Ionic Bonds: In ionic bonding, atoms transfer electrons to form ions with opposite charges. The transfer occurs from an atom with low ionization energy (tends to lose electrons) to an atom with high electron affinity (tends to gain electrons). The resulting oppositely charged ions are held together by electrostatic forces, creating an ionic compound. For example, sodium (Na) donates an electron to chlorine (Cl) to form sodium chloride (NaCl).
  • Covalent Bonds: In covalent bonding, atoms share electrons to achieve a stable electron configuration. This type of bonding typically occurs between nonmetals. The shared electrons are represented by pairs of dots or lines between the atoms. For example, in a molecule of water (H2O), oxygen shares electrons with two hydrogen atoms.

Kossel’s Theory of Chemical Bonding

Kossel’s theory of chemical bonding, also known as the electron transfer theory, was proposed by the German physicist Walther Kossel in the early 20th century. Kossel noticed that the highly electronegative halogens and the highly electropositive alkali metals are separated by noble gases and his theory focuses on the transfer of electrons between atoms as the basis for chemical bonding, particularly in ionic compounds. Koss el’s theory builds upon the concept of the octet rule and the key points of Kessel’s Theory of Chemical Bonding are as follows:

  • Electron Transfer: Kossel proposed that atoms form bonds by the complete transfer of electrons from one atom to another. This transfer occurs between an atom with low ionization energy (tends to lose electrons) and an atom with a high electron affinity (tends to gain electrons). The result is the formation of positively charged cations and negatively charged anions that are held together by electrostatic forces.
  • Ionic Bonding: Kossel’s theory emphasizes ionic bonding as the primary type of bonding in many compounds. It suggests that when an atom loses or gains electrons to achieve a stable electron configuration, it becomes an ion. The positively charged cations and negatively charged anions then attract each other, forming an ionic bond. This bonding occurs between metals and nonmetals.
  • Stability of Noble Gas Configuration: Kossel’s theory focuses on achieving a stable electron configuration similar to noble gases. By transferring or sharing electrons, atoms strive to attain a complete outer electron shell with eight valence electrons, except for hydrogen and helium, which can achieve stability with two valence electrons.

Fajan’s Rule

Fajan’s rule is postulated by Kazimierz Fajans in 1923. Fajans’ rule determines whether a chemical bond is covalent or ionic. He was able to predict ionic or covalent bonding at the time using X-ray crystallography and attributes such as ionic and atomic radius. The key points of Fajan’s rule are as follows:

  • Polarizing Power: Fajan’s rule states that cations with a higher charge or smaller size have greater polarizing power. A cation with a higher charge density, resulting from a higher charge or smaller size, can pull the shared electrons in a bond closer to itself, creating a more polar bond.
  • Polarizability: Fajan’s rule also considers the concept of polarizability, which refers to the ease with which the electron cloud of an atom or ion can be distorted. An anion with a larger size and more diffuse electron cloud is more easily polarized.
  • Ionic Character: According to Fajan’s rule, a chemical bond between a cation and an anion with high polarizing power and high polarizability respectively exhibits a greater degree of ionic character. In other words, the electrons in the bond are more localized towards the cation, creating a polar covalent or even an ionic bond.
  • Covalent Character: Conversely, a bond between species with low polarizing power and low polarizability tends to have a more covalent character. The electrons in the bond are more evenly shared between the atoms, resulting in a less polar or even nonpolar bond.

Examples of Fajan’s Rule

Some examples of Fajan’s Rule are as follows:

  • Sodium chloride (NaCl) has a low polarizing power cation (Na+) and a small polarizability anion (Cl–). Therefore, NaCl has a high degree of ionic character.
  • Magnesium oxide (MgO) has a high polarizing power cation (Mg2+) and a large polarizability anion (O2-). Therefore, MgO has a lower degree of ionic character and a higher degree of covalent character.
  • Aluminum iodide (AlI3) has a very high polarizing power cation (Al3+) and a very large polarizability anion (I–). Therefore, AII3 has a very low degree of ionic character and a very high degree of covalent character.

Types of Chemical Bonds

The strength and properties of the chemical bonds formed vary. There are four primary types of chemical bonds that atoms or molecules form to form compounds. Chemical bonds of this type are-

  • Ionic Bonds
  • Covalent Bonds
  • Hydrogen Bonds
  • Polar Bonds

Ionic Bonds

Ionic bonds are formed by the loss and gain of electrons. The atom which loses electrons is called a cation and is positively Charged while the atom which gains electrons is called an anion and is negatively charged. The Ionic bond is formed due to the electrostatic interaction between the cation and anion. Example – NaCl

Covalent Bonds

Covalent bonds are formed by the sharing of electrons. These types of bonds are formed when the atoms are not loose or gain electrons and hence they share their electrons with each other. The electrons of each atom revolve in the atom’s orbit as well as other atoms’ orbit with which the bond is formed.

Hydrogen Bonds

Polar Bonds are a type of covalent bond formed between two atoms due to the unequal distribution of electrons in the bond. The more electronegative atom attracts the shared pair of electrons within itself forming a slightly negative charge on the electronegative element and partially positive on the other bonded atom.

Sample Questions on Chemical Bonding

Question 1: Why do atoms react?

Answer:

Atoms with eight electrons in their final orbit are stable and do not react. Atoms with fewer than eight electrons react with other atoms to gain eight electrons in their outermost orbit and thus become stable.

Question 2: How do atoms react?

Answer:

Atoms in their final orbit with eight electrons are stable and do not react. Atoms with fewer than eight electrons react with other atoms, gaining eight electrons in their outermost orbit and becoming stable.

Question 3: What are the forces that keep reacting atoms together?

Answer:

Because the outer orbitals of atoms overlap in metals, the electrons present in them do not belong to any specific atom, but rather flow over to all atoms and bind them all together (metallic bonding). Atoms that lose and gain electrons combine to form ions, which are held together by electrostatic forces of attraction (Ionic Bond). When atoms give and share electrons equally, the shared electrons serve as a unifying force between them (covalent bond).

Question 4: What are hybridized orbitals?

Answer:

Relatively similar energy sub-orbitals can combine to generate a new set of the same number of orbitals, with all contributing orbitals having the feature of proportionality. They are called hybridized orbitals.

Question 5: Why is oxygen molecule paramagnetic?

Answer:

The oxygen molecule is formed when an oxygen atom shares two electrons with another oxygen atom. The oxygen molecule is paramagnetic, indicating that it contains unpaired electrons. To explain this, a molecular orbital theory has been proposed. According to this theory, atoms lose their orbitals and instead form an equal number of orbitals that cover the entire molecule, giving rise to the term molecular orbital. The filling of these orbitals in increasing energy order results in unpaired electrons, which explains the paramagnetic behaviour of the oxygen molecule.

FAQs on Chemical Bonding

Q1: Define Chemical Bonding.

Answer:

Chemical bonding refers to the attractive forces that hold atoms together in a molecule or compound. It involves the sharing, transfer, or redistribution of electrons between atoms to achieve a more stable electronic configuration.

Q2: What are the Different Types of Chemical Bonds?

Answer:

Different types of chemicals bonds are:

  • Ionic Bonds
  • Covalent Bonds
  • Hydrogen Bonds
  • Polar Bonds

Q3: What is an Ionic Bond?

Answer:

An ionic bond is a type of chemical bond formed between two atoms of significantly different electronegativities. One atom donates electrons (forming a cation) while the other accepts electrons (forming an anion), resulting in an electrostatic attraction between the oppositely charged ions.

Q4: What is a Covalent Bond?

Answer:

A covalent bond is a chemical bond formed by the sharing of electron pairs between atoms. It typically occurs between nonmetal atoms that have similar electronegativities, allowing them to share electrons and achieve a more stable electron configuration.

Q5: What is Electronegativity?

Answer:

Electronegativity is a measure of an atom’s ability to attract electrons towards itself in a chemical bond. It is based on the atom’s nuclear charge, distance from the valence electrons, and shielding effect of inner electrons. Electronegativity values help predict the type of bonding (ionic or covalent) that will occur between atoms.

Q6: How do you determine the Type of Bond formed between Two Atoms?

Answer:

The type of bond formed between two atoms depends on the difference in their electronegativities. If the electronegativity difference is large (typically >1.7), an ionic bond is formed. If the electronegativity difference is small (typically <1.7), a covalent bond is formed. Intermediate values may indicate a polar covalent bond.

Q7: Can Atoms form Multiple Bonds?

Answer:

Yes, atoms can form multiple bonds. For example, carbon can form four covalent bonds by sharing multiple electron pairs, as seen in molecules like methane (CH4) and ethene (C2H4).

Er. Neeraj K.Anand is a freelance mentor and writer who specializes in Engineering & Science subjects. Neeraj Anand received a B.Tech degree in Electronics and Communication Engineering from N.I.T Warangal & M.Tech Post Graduation from IETE, New Delhi. He has over 30 years of teaching experience and serves as the Head of Department of ANAND CLASSES. He concentrated all his energy and experiences in academics and subsequently grew up as one of the best mentors in the country for students aspiring for success in competitive examinations. In parallel, he started a Technical Publication "ANAND TECHNICAL PUBLISHERS" in 2002 and Educational Newspaper "NATIONAL EDUCATION NEWS" in 2014 at Jalandhar. Now he is a Director of leading publication "ANAND TECHNICAL PUBLISHERS", "ANAND CLASSES" and "NATIONAL EDUCATION NEWS". He has published more than hundred books in the field of Physics, Mathematics, Computers and Information Technology. Besides this he has written many books to help students prepare for IIT-JEE and AIPMT entrance exams. He is an executive member of the IEEE (Institute of Electrical & Electronics Engineers. USA) and honorary member of many Indian scientific societies such as Institution of Electronics & Telecommunication Engineers, Aeronautical Society of India, Bioinformatics Institute of India, Institution of Engineers. He has got award from American Biographical Institute Board of International Research in the year 2005.

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CBSE Class 11 Chemistry Syllabus

CBSE Class 11 Chemistry Syllabus is a vast which needs a clear understanding of the concepts and topics. Knowing CBSE Class 11 Chemistry syllabus helps students to understand the course structure of Chemistry.

Unit-wise CBSE Class 11 Syllabus for Chemistry

Below is a list of detailed information on each unit for Class 11 Students.

UNIT I – Some Basic Concepts of Chemistry

General Introduction: Importance and scope of Chemistry.

Nature of matter, laws of chemical combination, Dalton’s atomic theory: concept of elements,
atoms and molecules.

Atomic and molecular masses, mole concept and molar mass, percentage composition, empirical and molecular formula, chemical reactions, stoichiometry and calculations based on stoichiometry.

UNIT II – Structure of Atom

Discovery of Electron, Proton and Neutron, atomic number, isotopes and isobars. Thomson’s model and its limitations. Rutherford’s model and its limitations, Bohr’s model and its limitations, concept of shells and subshells, dual nature of matter and light, de Broglie’s relationship, Heisenberg uncertainty principle, concept of orbitals, quantum numbers, shapes of s, p and d orbitals, rules for filling electrons in orbitals – Aufbau principle, Pauli’s exclusion principle and Hund’s rule, electronic configuration of atoms, stability of half-filled and completely filled orbitals.

UNIT III – Classification of Elements and Periodicity in Properties

Significance of classification, brief history of the development of periodic table, modern periodic law and the present form of periodic table, periodic trends in properties of elements -atomic radii, ionic radii, inert gas radii, Ionization enthalpy, electron gain enthalpy, electronegativity, valency. Nomenclature of elements with atomic number greater than 100.

UNIT IV – Chemical Bonding and Molecular Structure

Valence electrons, ionic bond, covalent bond, bond parameters, Lewis structure, polar character of covalent bond, covalent character of ionic bond, valence bond theory, resonance, geometry of covalent molecules, VSEPR theory, concept of hybridization, involving s, p and d orbitals and shapes of some simple molecules, molecular orbital theory of homonuclear diatomic molecules(qualitative idea only), Hydrogen bond.

UNIT V – Chemical Thermodynamics

Concepts of System and types of systems, surroundings, work, heat, energy, extensive and intensive properties, state functions. First law of thermodynamics – internal energy and enthalpy, measurement of U and H, Hess’s law of constant heat summation, enthalpy of bond dissociation, combustion, formation, atomization, sublimation, phase transition, ionization, solution and dilution. Second law of Thermodynamics (brief introduction)
Introduction of entropy as a state function, Gibb’s energy change for spontaneous and nonspontaneous processes.
Third law of thermodynamics (brief introduction).

UNIT VI – Equilibrium

Equilibrium in physical and chemical processes, dynamic nature of equilibrium, law of mass action, equilibrium constant, factors affecting equilibrium – Le Chatelier’s principle, ionic equilibrium- ionization of acids and bases, strong and weak electrolytes, degree of ionization,
ionization of poly basic acids, acid strength, concept of pH, hydrolysis of salts (elementary idea), buffer solution, Henderson Equation, solubility product, common ion effect (with illustrative examples).

UNIT VII – Redox Reactions

Concept of oxidation and reduction, redox reactions, oxidation number, balancing redox reactions, in terms of loss and gain of electrons and change in oxidation number, applications of redox reactions.

UNIT VIII – Organic Chemistry: Some basic Principles and Techniques

General introduction, classification and IUPAC nomenclature of organic compounds. Electronic displacements in a covalent bond: inductive effect, electromeric effect, resonance and hyper conjugation. Homolytic and heterolytic fission of a covalent bond: free radicals, carbocations, carbanions, electrophiles and nucleophiles, types of organic reactions.

UNIT IX – Hydrocarbons

Classification of Hydrocarbons
Aliphatic Hydrocarbons:
Alkanes – Nomenclature, isomerism, conformation (ethane only), physical properties, chemical reactions.
Alkenes – Nomenclature, structure of double bond (ethene), geometrical isomerism, physical properties, methods of preparation, chemical reactions: addition of hydrogen, halogen, water, hydrogen halides (Markovnikov’s addition and peroxide effect), ozonolysis, oxidation, mechanism of electrophilic addition.
Alkynes – Nomenclature, structure of triple bond (ethyne), physical properties, methods of preparation, chemical reactions: acidic character of alkynes, addition reaction of – hydrogen, halogens, hydrogen halides and water.

Aromatic Hydrocarbons:

Introduction, IUPAC nomenclature, benzene: resonance, aromaticity, chemical properties: mechanism of electrophilic substitution. Nitration, sulphonation, halogenation, Friedel Craft’s alkylation and acylation, directive influence of functional group in monosubstituted benzene. Carcinogenicity and toxicity.

To know the CBSE Syllabus for all the classes from 1 to 12, visit the Syllabus page of CBSE. Meanwhile, to get the Practical Syllabus of Class 11 Chemistry, read on to find out more about the syllabus and related information in this page.

CBSE Class 11 Chemistry Practical Syllabus with Marking Scheme

In Chemistry subject, practical also plays a vital role in improving their academic scores in the subject. The overall weightage of Chemistry practical mentioned in the CBSE Class 11 Chemistry syllabus is 30 marks. So, students must try their best to score well in practicals along with theory. It will help in increasing their overall academic score.

CBSE Class 11 Chemistry Practical Syllabus

The experiments will be conducted under the supervision of subject teacher. CBSE Chemistry Practicals is for 30 marks. This contribute to the overall practical marks for the subject.

The table below consists of evaluation scheme of practical exams.

Evaluation SchemeMarks
Volumetric Analysis08
Salt Analysis08
Content Based Experiment06
Project Work04
Class record and viva04
Total30

CBSE Syllabus for Class 11 Chemistry Practical

Micro-chemical methods are available for several of the practical experiments. Wherever possible such techniques should be used.

A. Basic Laboratory Techniques
1. Cutting glass tube and glass rod
2. Bending a glass tube
3. Drawing out a glass jet
4. Boring a cork

B. Characterization and Purification of Chemical Substances
1. Determination of melting point of an organic compound.
2. Determination of boiling point of an organic compound.
3. Crystallization of impure sample of any one of the following: Alum, Copper Sulphate, Benzoic Acid.

C. Experiments based on pH

1. Any one of the following experiments:

  • Determination of pH of some solutions obtained from fruit juices, solution of known and varied concentrations of acids, bases and salts using pH paper or universal indicator.
  • Comparing the pH of solutions of strong and weak acids of same concentration.
  • Study the pH change in the titration of a strong base using universal indicator.

2. Study the pH change by common-ion in case of weak acids and weak bases.

D. Chemical Equilibrium
One of the following experiments:

1. Study the shift in equilibrium between ferric ions and thiocyanate ions by increasing/decreasing the concentration of either of the ions.
2. Study the shift in equilibrium between [Co(H2O)6] 2+ and chloride ions by changing the concentration of either of the ions.

E. Quantitative Estimation
i. Using a mechanical balance/electronic balance.
ii. Preparation of standard solution of Oxalic acid.
iii. Determination of strength of a given solution of Sodium hydroxide by titrating it against standard solution of Oxalic acid.
iv. Preparation of standard solution of Sodium carbonate.
v. Determination of strength of a given solution of hydrochloric acid by titrating it against standard Sodium Carbonatesolution.

F. Qualitative Analysis
1) Determination of one anion and one cation in a given salt
Cations‐ Pb2+, Cu2+, As3+, Al3+, Fe3+, Mn2+, Ni2+, Zn2+, Co2+, Ca2+, Sr2+, Ba2+, Mg2+, NH4 +
Anions – (CO3)2‐ , S2‐, NO2‐ , SO32‐, SO2‐ , NO ‐ , Cl‐ , Br‐, I‐, PO43‐ , C2O2‐ ,CH3COO‐
(Note: Insoluble salts excluded)

2) Detection of ‐ Nitrogen, Sulphur, Chlorine in organic compounds.

G) PROJECTS
Scientific investigations involving laboratory testing and collecting information from other sources.

A few suggested projects are as follows:

  • Checking the bacterial contamination in drinking water by testing sulphide ion
  • Study of the methods of purification of water.
  • Testing the hardness, presence of Iron, Fluoride, Chloride, etc., depending upon the regional
    variation in drinking water and study of causes of presence of these ions above permissible
    limit (if any).
  • Investigation of the foaming capacity of different washing soaps and the effect of addition of
    Sodium carbonate on it.
  • Study the acidity of different samples of tea leaves.
  • Determination of the rate of evaporation of different liquids Study the effect of acids and
    bases on the tensile strength of fibres.
  • Study of acidity of fruit and vegetable juices.

Note: Any other investigatory project, which involves about 10 periods of work, can be chosen with the approval of the teacher.

Practical Examination for Visually Impaired Students of Class 11

Below is a list of practicals for the visually impaired students.

A. List of apparatus for identification for assessment in practicals (All experiments)
Beaker, tripod stand, wire gauze, glass rod, funnel, filter paper, Bunsen burner, test tube, test tube stand,
dropper, test tube holder, ignition tube, china dish, tongs, standard flask, pipette, burette, conical flask, clamp
stand, dropper, wash bottle
• Odour detection in qualitative analysis
• Procedure/Setup of the apparatus

B. List of Experiments A. Characterization and Purification of Chemical Substances
1. Crystallization of an impure sample of any one of the following: copper sulphate, benzoic acid
B. Experiments based on pH
1. Determination of pH of some solutions obtained from fruit juices, solutions of known and varied
concentrations of acids, bases and salts using pH paper
2. Comparing the pH of solutions of strong and weak acids of same concentration.

C. Chemical Equilibrium
1. Study the shift in equilibrium between ferric ions and thiocyanate ions by increasing/decreasing
the concentration of eitherions.
2. Study the shift in equilibrium between [Co(H2O)6]2+ and chloride ions by changing the
concentration of either of the ions.

D. Quantitative estimation
1. Preparation of standard solution of oxalic acid.
2. Determination of molarity of a given solution of sodium hydroxide by titrating it against standard
solution of oxalic acid.

E. Qualitative Analysis
1. Determination of one anion and one cation in a given salt
2. Cations – NH+4
Anions – (CO3)2-, S2-, (SO3)2-, Cl-, CH3COO-
(Note: insoluble salts excluded)
3. Detection of Nitrogen in the given organic compound.
4. Detection of Halogen in the given organic compound.

Note: The above practicals may be carried out in an experiential manner rather than recording observations.

We hope students must have found this information on CBSE Syllabus useful for their studying Chemistry. Learn Maths & Science in interactive and fun loving ways with ANAND CLASSES (A School Of Competitions) App/Tablet.

Frequently Asked Questions on CBSE Class 11 Chemistry Syllabus

Q1

How many units are in the CBSE Class 11 Chemistry Syllabus?

There are 9 units in the CBSE Class 11 Chemistry Syllabus. Students can access various study materials for the chapters mentioned in this article for free at ANAND CLASSES (A School Of Competitions).

Q2

What is the total marks for practicals examination as per the CBSE Class 11 Chemistry Syllabus?

The total marks for the practicals as per the CBSE Class 11 Chemistry Syllabus is 30. It includes volumetric analysis, content-based experiment, salt analysis, class record, project work and viva.

Q3

Which chapter carries more weightage as per the CBSE Syllabus for Class 11 Chemistry?

The organic chemistry chapter carries more weightage as per the CBSE Syllabus for Class 11 Chemistry.

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