3. Atoms and Molecules-Laws of Chemical Combination Science Class 9 In English-CBSE Notes
Explore science cbse notes for Class 9 Chapter 3. Atoms and Molecules Topic Laws of Chemical Combination in English medium for exams preparation.
3. Atoms and Molecules-Laws of Chemical Combination Science Class 9 In English-CBSE Notes
Popular Topics Covered
Our study material includes
- cbse notes for class 9 science chapter 3. Atoms and Molecules topic Laws of Chemical Combination in english
- class 9 science chapter 3. Atoms and Molecules cbse notes
- cbse class 9 science chapter 3. Atoms and Molecules notes in english
- class 9 science chapter 3. Atoms and Molecules study notes
- class 9 science chapter 3. Atoms and Molecules revision notes
- cbse notes for class 9 science chapter 3. Atoms and Molecules
- class 9 science chapter 3. Atoms and Molecules summary notes
- cbse class 9 science chapter 3. Atoms and Molecules quick notes
All Topics Chapter 3. Atoms and Molecules
- 1. Laws of Chemical Combination
- 2. Ions And Atoms
- 3. Formation of Simple Molecules
- 4. Molecular Mass
- 5. Assignment
Notes
3. Atoms and Molecules-Laws of Chemical Combination Science Class 9 In English-CBSE Notes
3. Atoms and Molecules
Laws of Chemical Combination
3. Atoms And Molecules
Element: The basic substance of matter that can not be simplified is an element.
Example: Hydrogen, Carbon, Oxygen, Iron, Silver and Gold etc.
Atom: The smallest tiny particles of matter which cann't be divided further is called atom (Parmanu).
Molecules: A group of two or more than two atoms of the same element or different elements that chemically bonded together is called molecules.
Example: O2, H2, N2, H2O, CO2, MgCl2 etc.
Compound: A molecule that contains more than one element is compound.
Example: H2O, CO2, NH3, BrCl2, CH4 etc.
The smallest tiny particles of element is atom. like atom of Hydrogen (H), atom of oxygen (O), atom of Carbon (C), atom of Magnesium (Mg) etc.
So all matters are made by these tiny particles of elements i.e atoms.
Formation of Matter
Atoms of elements
⇓
Molecules Or atoms
⇓
Compounds
⇓
Matters
Laws of Chemical Combination:
The laws of chemical combination were established by Lavoisier and
Joseph L. Proust.
The laws of chemical combination are two;
1. Law of conservation of mass: Law of conservation of mass states that
mass can neither be created nor destroyed in a chemical reaction.
2. Law of constant proportions: In a chemical substance the elements are
always present in definite proportions by mass.
Dalton's Atomic Theory:
British chemist John Dalton provided the basic theory about the nature of matter.
Dalton picked up the idea of divisibility of matter, which was till then just a philosophy. He took the name ‘atoms’ as given by the Greeks and said that the smallest particles of matter are atoms. His theory was based on the laws of chemical combination.
The postulates of dalton's theory:
(i) All matter is made of very tiny particles called atoms.
(ii) Atoms are indivisible particles, which cannot be created or destroyed in a
chemical reaction.
(iii) Atoms of a given element are identical in mass and chemical properties.
(iv) Atoms of different elements have different masses and chemical properties.
(v) Atoms combine in the ratio of small whole numbers to form compounds.
(vi) The relative number and kinds of atoms are constant in a given compound.
The name of elements and its symbol:
IUPAC (International Union of Pure and Applied Chemistry) approves names
of elements. Many of the symbols are the first one or two letters of the element’s name in English. The first letter of a symbol is always written as a capital letter (uppercase) and the second letter as a small letter (lowercase).
Example:
Hydrogen: H
Carbon : C
Aluminium: Al
Magnesium: Mg
Symbols of some elements are formed from the first letter of the name and a letter, appearing later in the name. Examples are:
(i) chlorine, Cl,
(ii) zinc, Zn etc.
Each element has a name and a unique chemical symbol.
Some examples of elements and their symbol.
Atomic Mass: An atomic mass unit or amu is one twelfth of the mass of an unbound atom of carbon -12 isotope. This is approximetely 1.67377 x 10 -27 kilogram (kg).
The relative atomic mass of the atom of an element is defined as the average mass of the atom, as compared to 1/12th the mass of one carbon-12 atom.
Atomic mass unit is abbreviated as 'amu' but on IUPAC latest recommendation, it is writen as 'u'.
Existance of atoms:
Atoms never exist independly. They form molecules or ions.
We can say, atoms exist in group.
All Topics Chapter 3. Atoms and Molecules
3. Atoms and Molecules-Laws of Chemical Combination Science Class 9 In English-CBSE Notes
Hindi Medium Students/Teachers/Tutors:
All Chapters science Class 9
CBSE Notes for Class 9 science Chapter 3. Atoms and Molecules – Laws of Chemical Combination
The CBSE Notes for Class 9 science Chapter 3. Atoms and Molecules – Laws of Chemical Combination are prepared to help students understand every concept in a simple, clear, and well-organized manner. These notes are based on the latest CBSE syllabus and are suitable for regular classroom learning, homework, revision, and examination preparation. Every topic is explained using easy language so that students can learn important concepts without difficulty and develop a strong academic foundation.
Studying directly from the textbook is essential, but during revision students often need concise study material that highlights only the most important information. These chapter-wise notes provide exactly that. Instead of reading lengthy chapters repeatedly, students can quickly revise definitions, concepts, facts, examples, and important points in a short period of time. This approach saves valuable study time while improving understanding and retention.
Why Study Chapter 3. Atoms and Molecules – Laws of Chemical Combination Using Our Notes?
Every chapter contains several important concepts that require careful understanding. Our notes present these concepts in a logical sequence so students can connect ideas easily. Difficult topics are simplified with easy explanations, making learning enjoyable for students of different learning abilities. Whether you are preparing for classroom discussions, assignments, periodic tests, or annual examinations, these notes provide a reliable source for effective revision.
- Prepared according to the latest CBSE curriculum.
- Simple and student-friendly explanations.
- Chapter-wise organized content for easy learning.
- Important concepts, definitions, and key points included.
- Useful for quick revision before examinations.
- Supports self-study and classroom learning.
- Helps improve conceptual understanding and confidence.
- Suitable for homework, assignments, and test preparation.
Benefits of Reading CBSE Notes Regularly
Consistent revision is one of the most effective ways to achieve academic success. Reading CBSE Notes for Class 9 science Chapter 3. Atoms and Molecules – Laws of Chemical Combination regularly helps students remember important information for a longer period. Since the content is arranged systematically, students can identify important topics quickly and revise them whenever required.
These notes also help students improve answer-writing skills by presenting information in a structured format. Instead of memorizing lengthy paragraphs, students learn how to organize answers using important points and concepts. This not only improves writing quality but also increases confidence during examinations.
How to Use These Notes Effectively
To get the best results, students should first read the NCERT textbook carefully and understand the chapter. After completing the textbook, they should study these notes to reinforce important concepts. During revision, students can focus on highlighted definitions, important facts, and key ideas before solving textbook exercises and practice questions. This learning strategy improves both understanding and long-term memory.
Teachers and parents can also use these notes as a quick reference while helping students revise lessons or complete assignments. Since the content is concise and well-organized, it becomes easier to explain difficult topics within a limited amount of time.
Features of Our CBSE Notes
Every chapter on our platform is created with the objective of making learning easier for students. Our educational team regularly reviews and updates the content according to the latest CBSE guidelines so that students always receive reliable and accurate study material.
- Easy-to-understand chapter explanations.
- Important definitions and key concepts.
- Well-structured content for faster revision.
- Based on the latest CBSE syllabus.
- Helpful for school exams and annual examinations.
- Free online access on desktop and mobile devices.
Prepare Better with Chapter-wise CBSE Notes
Success in examinations depends on consistent practice and smart revision. These CBSE Notes for Class 9 science Chapter 3. Atoms and Molecules – Laws of Chemical Combination are designed to reduce study pressure by presenting important information in a concise and meaningful way. Students can use them throughout the academic session for daily learning as well as last-minute revision before examinations.
Along with these notes, students are encouraged to solve NCERT textbook questions, practice important questions, and attempt sample papers regularly. Combining concept-based learning with regular practice helps improve problem-solving ability, analytical thinking, and overall academic performance. With disciplined study habits and quality learning resources, students can build confidence, strengthen their understanding of every chapter, and achieve excellent results in school examinations.
3. Atoms and Molecules-Laws of Chemical Combination Science Class 9 In English-CBSE Notes Study Materials For Class 6 to 12
If you want to improve your academic performance, start studying with free CBSE notes for all classes. These notes are designed to make learning simple, clear, and effective for every student. Choose your class, explore the chapters, and begin your preparation with the latest cbse notes today.
