In the year 1808, the English scientist and chemist John Dalton proposed Dalton’s atomic hypothesis, a scientific theory on the nature of matter. It asserted that all matter is made up of atoms, which are tiny, indivisible units.
According to Dalton’s atomic theory, all substances are made up of atoms, which are indestructible and indivisible building blocks. While the atoms of one element were all the same size and mass, other elements had atoms of different sizes and weights.
What is Atomic Theory?
Atomic theory is a fundamental concept in science that describes matter as composed of discrete units called atoms.
Atoms are the smallest particles of an element that maintain the chemical properties of that element.
They consist of a nucleus containing protons and neutrons, surrounded by electrons in various orbits.
This theory explains the behavior of atoms in chemical reactions, where they rearrange to form new substances without being destroyed or fundamentally altered. Initially proposed by John Dalton in the early 19th century, atomic theory has evolved to incorporate the discovery of subatomic particles and the principles of quantum mechanics, profoundly impacting our understanding of chemistry and physics.
Postulates of Dalton’s Atomic Theory
The postulates of Dalton’s theory may be stated as follows:
All matter is composed of atoms, which are indivisible: According to Dalton, the law of conservation of mass and the law of definite proportions can be explained using the idea of atoms. He proposed that all matter is made of tiny indivisible particles called atoms, which he imagined as “solid and movable particles”
All atoms of a given element are identical in mass and properties: Dalton proposed that every single atom of a particular element, such as copper, potassium etc, is the same as every other atom of that particular element. e.g. A potassium atom is different from an oxygen atom. Elements may share some similar boiling points, melting points, but no two elements have the same exact same set of properties.
Compounds are combinations of two or more different types of atoms: In the third part of Dalton’s atomic theory, he proposed that compounds are combinations of two or more different types of atoms. An example of such a compound is Common Salt. Common Salt is a combination of two different types of elements with varying physical and chemical properties. The first, sodium, is a highly reactive metal. The second, chlorine, is a toxic gas. When they react, the atoms combine in a 1:1 ratio to form white crystals of NaCl.
A chemical reaction is a rearrangement of atoms: In the last postulate, Dalton suggested that chemical reactions neither destroy and nor create atoms. They just rearranged the atoms. Using our salt example again, when sodium combines with chlorine to make salt, both the sodium and chlorine atoms still exist. They simply rearrange to form a new compound.
Advantages of Dalton’s Atomic Theory:
Dalton’s theory provides a basic idea to differentiate between elements and compounds.
Dalton’s atomic theory. doesn’t violate the law of multiple proportions, the law of conservation of mass, and the law of constant proportions.
Disadvantages of Dalton’s Atomic Theory:
Dalton states that atoms are indivisible that they can be further divided into electron, proton and neutron.
Dalton states that atoms of a given element have exactly the same masses. But, it is known that even atoms of the same element can have different masses just like isotopes.
Dalton states that atoms of different elements can have different masses. But, it is known that even atoms of different element can have same masses just like isobars.
For scientific lovers, one of the most significant areas of inquiry has been mattering. Scientists and philosophers have long sought to make things easier to understand. They were curious about the fundamental particles that make up matter, as well as its properties, structure, and other characteristics. As a result, a variety of atomic theories were developed.
Democritus is credited as being the first to postulate that matter is made up of particles. These particles were given the name atomos, which means indivisible in Greek. Democritus’ Atomic Theory was based on this. Scientists had very little information on this idea at the time due to a lack of technical setup.
Scientist John Dalton manifested the works on simplifying matter over two thousand years later. John Dalton proposed the famous Dalton’s Atomic Theory in 1808. In a paper titled “A New Chemical Philosophy,” he published this idea; certainly, the philosophy was novel at the time. Let’s have a look at the theory’s postulates.
Dalton formulated his theory based on two laws: the law of conservation of mass and the law of constant composition.
Law of Conservation of Mass: In 1789, Antoine Laurent Lavoisier discovered the law of conservation of mass. The law of conservation of mass says that matter can neither be not created nor destroyed but it can modified from one for to another in a closed system. We use the law of conservation of mass to balance linear equations.
Law of Constant Composition: The law of constant composition says that a pure compound will always have the same proportion of the same elements. For example, table salt, which has the molecular formula NaCl contains the same proportions of sodium and chlorine instead of the fact, how much salt we want to make.
Limitations of Dalton’s Atomic Theory
Subatomic Particles: Dalton’s atomic theory posited that atoms were indivisible. This has been disproven with the discovery of subatomic particles—protons, electrons, and neutrons—which make up atoms.
Isotopes: Dalton believed all atoms of a given element were identical in mass and properties. However, isotopes, which are variants of elements with different atomic masses, contradict this idea. Examples include hydrogen, deuterium, and tritium, each having different numbers of neutrons.
Isobars: Dalton’s theory also claimed that atoms of different elements would have different masses. Yet, isobars, atoms of different elements that share the same mass number (such as 40Ar and 40Ca), demonstrate this is not necessarily true.
Combination Ratios: Dalton suggested that elements combine in simple whole-number ratios to form compounds. However, many complex organic compounds, like sugar, do not conform to simple stoichiometric ratios.
Allotropes: The theory does not explain allotropes—different forms of the same element with distinct properties, such as carbon manifesting as both diamond and graphite.
Sample Questions on Dalton’s Atomic Theory
Question 1: Whether it is possible that a molecule is made up of a single atom?
Answer:
An electrically neutral group of two or more atoms held together by chemical bonds is the most basic definition of molecule. In that sense, no, by nature, a molecule can not be formed from a single atom.
Question 2: Is Salt (NaCl) a molecule?
Answer:
Molecules are subject to molecular bonds. Something like table salt (NaCl) is a compound because it is made of more than one type of element (sodium and chlorine), but it is not a molecule because it is an ionic bond that holds NaCl together. We can say sodium chloride is an ionic compound.
Question 3: What is the difference between atoms and molecules?
Answer:
A tiny particle of a chemical element is called an atom, which may or may not exist independently. Molecules refer to the group of atoms that the bond binds together, representing the smallest unit in a compound. Two or more identical or distinct atoms are chemically bonded.
Question 4: What is the mass number?
Answer:
The complete amount is in the protons and neutrons in the nucleus of an atom. For example, nitrogen has seven protons in its nucleus and seven neutrons, supplying it with 14 masses.
Question 5: Who discovered the atomic number?
Answer:
The number of protons (positive charges) in the nucleus of an atom is given by its atomic number. This term was first introduced by Henry Gwyn-Jefferies Moseley.
Question 6: Do protons and electrons have the same mass?
Answer:
Electrons are a sort of negative-charged subatomic particle. Protons and neutrons have about the same mass as electrons, yet they are both significantly more massive (approximately 2,000 times as massive as an electron). A proton’s positive charge is the same magnitude as an electron’s negative charge.
Dalton’s Atomic Theory – FAQs
What are the main postulates of Dalton’s Atomic Theory?
All matter is composed of indivisible and indestructible atoms.
All atoms of a given element are identical in mass and properties, while atoms of different elements differ in mass and properties.
Atoms combine in simple whole-number ratios to form compounds.
Chemical reactions involve rearrangement, separation, or combination of atoms; atoms themselves are not created or destroyed in chemical reactions.
What are the Merits of Dalton’s Atomic Theory?
Foundation for Modern Chemistry: Shifted atomic concepts from philosophical to scientific grounds.
Explained Chemical Laws: Supported laws of conservation of mass, definite proportions, and multiple proportions.
Differentiated Elements and Compounds: Clarified differences, foundational for chemical studies.
Introduced Chemical Formulas: Laid groundwork for using formulas to represent chemical compounds.
Stimulated Further Research: Though partly incorrect, spurred advances in atomic structure and subatomic discoveries.
What were the limitations of Dalton’s Atomic Theory?
The theory incorrectly stated that atoms were indivisible. Subatomic particles like protons, neutrons, and electrons were later discovered.
Dalton’s theory did not account for isotopes, which are atoms of the same element with different masses.
It failed to explain the existence of isobars—atoms of different elements with the same mass.
The theory did not acknowledge the formation of non-stoichiometric compounds, nor did it account for allotropes like the different forms of carbon (graphite, diamond, etc.).
Who disproved parts of Dalton’s Theory?
J.J. Thomson disproved the idea that atoms are indivisible. He discovered electrons and proposed a model of the atom with a central nucleus and electrons orbiting it, significantly advancing our understanding of atomic structure.
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.
Anand Technical Publishers
Buy Products (Printed Books & eBooks) of Anand Classes published by Anand Technical Publishers, Visit at following link :
