CBSE 9 Science | 3. Atoms and Molecules by Akhil | Learn Smarter
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3. Atoms and Molecules

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Sections

  • 3

    Atoms And Molecules

    The section discusses the foundational concepts of atoms and molecules, including the laws of conservation of mass and constant proportions, and introduces Dalton's atomic theory.

    Learning Practice

  • 3.1

    Laws Of Chemical Combination

    The section discusses the fundamental laws governing chemical combinations, namely the Law of Conservation of Mass and the Law of Constant Proportions.

    Learning Practice

  • 3.1.1

    Law Of Conservation Of Mass

    The Law of Conservation of Mass states that mass is neither created nor destroyed in a chemical reaction.

    Learning Practice

  • 3.1.2

    Law Of Constant Proportions

    The Law of Constant Proportions states that in a chemical compound, elements combine in fixed ratios by mass.

    Learning Practice

  • 3.2

    What Is An Atom?

    This section introduces the concept of atoms as the fundamental building blocks of matter, detailing their properties, symbols, and significance in chemical reactions.

    Learning Practice

  • 3.2.1

    What Are The Modern Day Symbols Of Atoms Of Different Elements

    This section discusses the historical development and modern representation of atomic symbols for different elements.

    Learning Practice

  • 3.2.2

    Atomic Mass

    This section discusses the concept of atomic mass and highlights its significance in atomic theory.

    Learning Practice

  • 3.2.3

    How Do Atoms Exist

    Atoms of most elements cannot exist independently; they form molecules or ions that aggregate to create matter.

    Learning Practice

  • 3.3

    What Is A Molecule?

    A molecule is defined as a group of two or more atoms that are chemically bonded together, representing the smallest particle of an element or compound capable of independent existence.

    Learning Practice

  • 3.3.1

    Molecules Of Elements

    This section explains the concept of molecules, particularly focusing on how elements are composed of molecules formed from the same type of atoms.

    Learning Practice

  • 3.3.2

    Molecules Of Compounds

    Compounds are formed when atoms of different elements combine in fixed proportions, resulting in unique chemical structures and properties.

    Learning Practice

  • 3.3.3

    What Is An Ion?

    This section discusses the concept of ions in compounds formed from metals and non-metals, expounding on the terms anions, cations, and polyatomic ions.

    Learning Practice

  • 3.4

    Writing Chemical Formulae

    This section introduces the rules for writing chemical formulae of compounds based on the valencies and combinations of elements.

    Learning Practice

  • 3.4.1

    Formulae Of Simple Compounds

    This section explains the concept of binary compounds, their valency, and how to write chemical formulae for simple compounds.

    Learning Practice

  • 3.5

    Molecular Mass

    Molecular Mass refers to the sum of the atomic masses of all atoms in a molecule, expressed in atomic mass units (u).

    Learning Practice

  • 3.5.1

    Molecular Mass

    This section introduces the concept of molecular mass, explaining how it can be calculated by summing the atomic masses of the atoms present in a molecule.

    Learning Practice

  • 3.5.2

    Formula Unit Mass

    This section introduces the concept of formula unit mass, explaining how to calculate it and its relationship with molecular mass.

    Learning Practice

References

NCERT Study Material

Class Notes

Memorization

Revision Tests

Chapter FAQs