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Revision Notes

Journey Inside the Atom

CBSE · Class 9 · Science

Quick revision notes for Journey Inside the Atom — CBSE Class 9 Science. Key concepts, formulas, and definitions for last-minute revision.

111 questions72 flashcards5 concepts

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Key Topics to Revise

1

1. Origin and Development of Atomic Ideas

  • Acharya Kanada suggested that matter divided repeatedly reaches the smallest particles called parmanus.
  • Leucippus and Democritus suggested indivisible particles called atomos, meaning indivisible.
  • These early ideas were imaginary and not based on experiments.
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2. Discovery of Subatomic Particles and Atomic Models

  • J. J. Thomson discovered the electron in 1897 using cathode ray tube experiments.
  • The electron has a negative charge of -1.602 × 10^-19 C, but it is taken as -1 by convention.
  • Thomson proposed the plum pudding model, also compared to a watermelon.
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3. Atomic Number, Mass Number, and Electronic Configuration

  • Atomic number (Z) is the number of protons in the nucleus.
  • For a neutral atom, number of protons equals number of electrons.
  • Hydrogen has atomic number 1 with 1 proton and 1 electron, and no neutron.
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4. Isotopes, Isobars, and Atomic Mass

  • Atoms of the same element can have different numbers of neutrons.
  • Isotopes are atoms of the same element with the same atomic number but different mass numbers.
  • Protium, deuterium, and tritium are isotopes of hydrogen.

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Full Notes

Key Concepts

Acharya Kanada proposed indivisible particles calledDalton proposed in 1808 that matterJThomson described the atom asGeiger and Marsden worked under Rutherford

Frequently Asked Questions

What are the important topics in Journey Inside the Atom for CBSE Class 9 Science?
Key topics in Journey Inside the Atom include Force and Laws of Motion — Complete Concept Map, Correct vs Incorrect Understanding of Newton's First Law, Chapter Overview — Force and Laws of Motion. These are the concepts CBSE Class 9 examiners draw on most — study them first, then practise related questions.
How to score full marks in Journey Inside the Atom — CBSE Class 9 Science?
Understand the core concepts first, then work through the 111 practice questions available for this chapter. Revise formulas and definitions regularly, and use flashcards for quick recall before the exam.

Sources & Official References

Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.

More resources for Journey Inside the Atom

All 13 chapters — CBSE Class 9 Science Revision Notes

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