A covalent bond is formed by the equal sharing of electrons from both participating atoms. The pair of electrons participating in this type of bonding is called a shared pair or bonding pair.
Covalent bonds are also called molecular bonds. Sharing of bonding pairs will ensure that the atoms achieve stability in their outer shell, which is similar to the atoms of noble gases.
Table of Contents
What Is Covalent Bond?
Elements having very high ionisation energies are incapable of transferring electrons, and elements having very low electron affinity cannot take up electrons.
The atoms of such elements tend to share their electrons with the atoms of other elements or with other atoms of the same element in a way that both the atoms obtain octet configuration in their respective valence shells, and thus achieve stability.
Such association through sharing of electron pairs among different or same kinds is known as Covalent Bond.
Formation of Covalent Bond
Covalent bonding can be achieved in two ways:
Sharing of electrons between atoms of the same kind, for example, formation of H2, Cl2, O2, etc.
Sharing of electrons between atoms of different kinds, for example, formation of CH4, H2O, NH3, etc.
Covalent Bonding in Carbon Atom
As per the electronic configuration of carbon, it needs to gain or lose 4 electrons to become stable, which seems impossible as:
Carbon cannot gain 4 electrons to become C4-, because it will be tough for 6 protons to hold 10 electrons, and so the atom will become unstable.
Carbon cannot lose 4 electrons to become C4+ because it would require a large amount of energy to remove out 4 electrons. Also, the C4+ would have only 2 electrons held by the proton, which will again become unstable.
Carbon cannot gain or donate electrons, so to complete its nearest noble gas configuration, it shares electrons to form a covalent bond.
Properties of Covalent Bond
If the normal valence of an atom is not satisfied by sharing a single electron pair between atoms, the atoms may share more than one electron pair between them. Some of the properties of covalent bonds are listed below:
Covalent bonding does not result in the formation of new electrons. The bond only pairs them.
They are very powerful chemical bonds that exist between atoms.
A covalent bond normally contains an energy of about ~80 kilocalories per mole (kcal/mol).
Covalent bonds rarely break spontaneously after it is formed.
Covalent bonds are directional, where the atoms that are bonded showcase specific orientations relative to one another.
Most compounds having covalent bonds exhibit relatively low melting points and boiling points.
Compounds with covalent bonds usually have lower enthalpies of vaporisation and fusion.
Compounds formed by covalent bonding don’t conduct electricity due to the lack of free electrons.
Covalent compounds are not soluble in water.
What Is the Octet Rule?
All atoms except noble gases have less than eight electrons in their valence shell. In other words, the valence shells of these atoms do not have stable configurations. Therefore, they combine with each other or with other atoms to attain stable electronic configurations.
Therefore,
“The tendency of atoms of various elements to attain stable configuration of eight electrons in their valence shells is the cause of chemical combination”
and
“The principle of attaining the maximum of eight electrons in the valence shell of atoms is called the octet rule.”
Lewis introduced simple symbols to denote the electrons present in the outer shell of an atom known as the valence electrons. These symbols are known as Electron Dot Symbols, and the structure of the compound is known as Lewis Dot Structure.
Dot structure of methane
Conditions for Writing the Lewis Dot Structures
Sharing of an electron pair between the atoms results in the formation of covalent bonds.
During bond formation, each bond consists of two electrons which are contributed by each one of the combining atoms.
By the mutual sharing of electrons, each atom attains an octet configuration in its valence shell.
Electron dot structures of covalent molecules are written with respect to the octet rule. According to this rule, all the atoms in the molecule will have eight electrons in their valence shell except the hydrogen atom. Hydrogen will have only two electrons because only two electrons complete its first shell to attain helium configuration.
Thus the elements of group 17, such as Cl, would share one electron to attain a stable octet; the elements of group 16, such as O and S, would share two electrons; the elements of group 15 would share three electrons and so on.
For Example, the oxygen atom, which has six electrons in its valence shell, completes its octet by sharing its two electrons with two hydrogen atoms to form a water molecule.
Lewis Structure of Water Molecule
Types of Covalent Bonds
Depending upon the number of shared electron pairs, the covalent bond can be classified into:
Single Covalent Bond
Double Covalent Bond
Triple Covalent Bond
Single Bonds
A single bond is formed when only one pair of electrons is shared between the two participating atoms. It is represented by one dash (-). Although this form of covalent bond has a smaller density and is weaker than a double and triple bond, it is the most stable.
For example, the HCL molecule has one hydrogen atom with one valence electron and one chlorine atom with seven valence electrons. In this case, a single bond is formed between hydrogen and chlorine by sharing one electron.
Double Bonds
A double bond is formed when two pairs of electrons are shared between the two participating atoms. It is represented by two dashes (=). Double covalent bonds are much stronger than single bonds, but they are less stable.
For example, a carbon dioxide molecule has one carbon atom with six valence electrons and two oxygen atoms with four valence electrons.
To complete its octet, carbon shares two of its valence electrons with one oxygen atom and two with another oxygen atom. Each oxygen atom shares its two electrons with carbon, and therefore there are two double bonds in CO2.
CO2 Molecule with Double Covalent Bond
Oxygen Molecule: In the formation of the oxygen molecule, each oxygen atom has six electrons in its valence shell. Each atom requires two more electrons to complete its octet. Therefore, the atoms share two electrons each to form the oxygen molecule. Since two electron pairs are shared, there is a double bond between the two oxygen atoms.
O2 Molecule with Double Covalent Bond
Ethylene Molecule: In ethylene, each carbon atom shares two of its valence electrons with two hydrogen atoms and the remaining two electrons with the other carbon atom. So, there is a double bond between the carbon atoms.
Double Bond in Ethylene Molecule
Triple Bond
A triple bond is formed when three pairs of electrons are shared between the two participating atoms. Triple covalent bonds are represented by three dashes (≡) and are the least stable type of covalent bonds.
For example, in the formation of a nitrogen molecule, each nitrogen atom having five valence electrons provides three electrons to form three electron pairs for sharing. Thus, a triple bond is formed between the two nitrogen atoms.
Nitrogen Molecule with Triple Bond
Polar Covalent Bond
This type of covalent bond exists where the unequal sharing of electrons occurs due to the difference in the electronegativity of combining atoms. More electronegative atoms will have a stronger pull for electrons. The electronegative difference between the atoms is greater than zero and less than 2.0. As a result, the shared pair of electrons will be closer to that atom.
For example, molecules form hydrogen bonding as a result of an unbalanced electrostatic potential. In this case, the hydrogen atom interacts with electronegative fluorine, hydrogen, or oxygen.
Nonpolar Covalent Bond
This type of covalent bond is formed whenever there is an equal share of electrons between atoms. The electronegativity difference between two atoms is zero. It occurs wherever the combining atoms have similar electron affinity (diatomic elements).
For example, Nonpolar Covalent Bond is found in gas molecules like hydrogen gas, nitrogen gas, etc.
Polarization of Covalent Bonds
It is observed that in the sigma bonds between two different atoms, the electron cloud is always closer to the more electronegative of the two atoms participating in the sigma bond. Due to this, there is a permanent dipole that arises in the bond, and the covalent bond is said to be polarized.
Polarity of Covalent Bond in Water Molecule
An illustration describing the polarity of the covalent bonds in a water molecule is provided above. The more electronegative atom is said to have a partial negative charge, and the less electronegative atom has a partial positive charge in the polar covalent bond.
Difference between Covalent and Ionic Bonds
Covalent bonds and ionic bonds are types of atomic bonds. These bonds are different in their properties and structure. Covalent bonds include pairs of electrons by two atoms binding them in a fixed orientation, while a bond between two ions is called an ionic bond.
Covalent vs Ionic Bonds
Covalent bonding occurs between two non-metallic atoms, characterised by the sharing of electron pairs between the atoms and other covalent bonds with an electronegativity difference greater than 2.0 (<2.0). In the case of covalent bond formation, polyatomic ions are formed, whereas the ionic bond is formed as a result of electrostatic attraction between the oppositely charged ions.
Ionic Bond vs Covalent Bond
Difference between Ionic and Covalent Bond
Covalent Bonds
Ionic Bonds
A covalent bond is formed between two similar electronegative non-metals
This type of bond is formed between a metal and non-metal
Bonds formed from covalent bonding have a definite shape
Ionic bonds have no definite shape
Low melting point and boiling point
High melting point and boiling point
Low polarity and more flammable
High polarity and less flammable
Covalent bonds are in a liquid or gaseous state at room temperature
At room temperature, ionic bonds have a solid state.
Examples: Methane, Hydrochloric acid
Examples: Sodium chloride, Sulfuric Acid
The presence of a bond between two elements can be determined by calculating the electronegative value between two atoms.
Bond Type
Electronegativity Value
Polar Covalent Bond
0.5 to 1.9
Non-polar Covalent Bond
0 to 0.4
Ionic Bond
2.4 to 4.0
Solved Examples
1. Which of the following compounds contains both covalent and ionic bonds?
a. NaOH
b. NaBr
c. NaNC
d. NaCN
Answer: (c) NaNC
A covalent bond is present between N and C Atom, and an ionic bond is present between the Na+ ion and –NC ion.
2. A chemical bonding between the two atoms which shares a single pair of an electron is
a. Ionic bond
b. Single bond
c. Double bond
d. Triple bond
Answer: (b) Single bond
3. Which of the following compounds contains both polar and non-polar covalent bonds?
a. NH4Br
b. H2O2
c. CH4
d. HF
Answer: (b) H2O2
In H2O2, the electronegativity difference between o and H atoms is 1.4, so O – H bond is polar.
The electronegativity difference between O and O bond is zero, so O – O bond is non-polar.
4. Draw the Lewis structure of:
Carbon Tetrachloride (CCl4)
Ammonia (NH3)
1. Carbon has four electrons in its valence shell and completes its octet by sharing its four electrons with four chlorine atoms to form a carbon tetrachloride (CCl4) molecule, as shown below.
2. Nitrogen has five electrons in its valence shell and completes its octet by sharing its three electrons with three hydrogen atoms to form NH3 (Ammonia).
Lewis Structure of Ammonia (NH3)
Neeraj Anand, Param Anand
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.
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 Scheme
Marks
Volumetric Analysis
08
Salt Analysis
08
Content Based Experiment
06
Project Work
04
Class record and viva
04
Total
30
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 theapproval 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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