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Journey Inside the Atom — Revision Notes

CBSE · Class 9 · Science

Journey Inside the Atom revision notes for CBSE Class 9 Science: 4 topics in quick points. Part of the CBSE Class 9 Science syllabus.

111 questions72 flashcards2 formulas & key relations5 concepts

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Key Topics to Revise

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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 Origin and Development of Atomic Ideas, Discovery of Subatomic Particles and Atomic Models, Atomic Number, Mass Number, and Electronic Configuration, Isotopes, Isobars, and Atomic Mass. Study these first, then practise questions on each for Class 9 exams.
How should I revise Journey Inside the Atom for Class 9 exams?
Learn the core ideas first, then work through the 111 practice questions on Journey Inside the Atom. Revise 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 CBSE Class 9 Science Revision Notes

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