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Structure of the Atom

CBSE · Class 9 · Science

Complete topic list for Structure of the Atom in CBSE Class 9 Science. Key concepts, sub-topics, and what to focus on for board exams.

44 questions24 flashcards5 concepts

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An illustration of J.J. Thomson's atomic model, depicting an atom as a sphere of uniformly distributed positive charge with electrons (plums) embedded within it.
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4 Topics · CBSE Class 9 Science

Topics in Structure of the Atom

1

Discovery of Sub-atomic Particles

  • Atoms are not indivisible but contain smaller particles called sub-atomic particles
  • Three main sub-atomic particles: electrons, protons, and neutrons
  • J.J. Thomson discovered electrons in 1897 using cathode ray tube experiments
2

Atomic Models

  • Thomson's Model (1904): 'Plum pudding' or 'watermelon' model - electrons embedded in positive sphere
  • Rutherford's Model (1911): Nuclear model with electrons revolving around nucleus
  • Rutherford's alpha particle scattering experiment revealed the nucleus
3

Electronic Configuration and Bohr-Bury Rules

  • Electrons are arranged in shells or energy levels around the nucleus
  • Shells are designated as K, L, M, N or n = 1, 2, 3, 4
  • Maximum electrons in shell = 2n² where n is shell number
4

Valency

  • Valency is the combining capacity of an atom
  • Determined by the number of valence electrons
  • Atoms tend to achieve stable electronic configuration (octet in outermost shell)

Key Concepts

Atoms contain three fundamental particlesProposed that atoms are like ChristmasBased on alphaElectrons revolve in fixed orbits (KElectrons fill shells following rules

Frequently Asked Questions

What are the important topics in Structure of the Atom for CBSE Class 9 Science?
Structure of the Atom covers several key topics that are frequently asked in CBSE Class 9 board exams. Focus on the core concepts listed on this page and practise related questions to build confidence.
How to score full marks in Structure of the Atom — CBSE Class 9 Science?
Understand the core concepts first, then work through the 44 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.

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