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What is inside the atom — Syllabus

Telangana Board · Class 9 · Physical Science

What is inside the atom topics: Discovery of Sub-atomic Particles, Atomic Models - Evolution, Electronic Configuration and Bohr-Bury, plus 1 more.

45 questions24 flashcards3 formulas & key relations5 concepts

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4 Topics · Telangana Board Class 9 Physical Science · 2026-27

Topics in What is inside the atom

1

Discovery of Sub-atomic Particles

  • Michael Faraday's electrolysis experiments showed that atoms could gain or lose charges, contradicting Dalton's theory of indivisible atoms
  • J.J. Thomson discovered electrons in 1897 using cathode ray tube experiments - first sub-atomic particle discovered
  • Electrons are negatively charged particles with negligible mass (1/1836th of proton mass)
2

Atomic Models - Evolution of Understanding

  • Thomson's 'Plum Pudding' Model (1898): Atom as sphere of positive charge with electrons embedded like plums in pudding
  • Rutherford's Gold Foil Experiment (1909): α-particles fired at thin gold foil to study atomic structure
  • Rutherford's observations: Most α-particles passed through, few deflected at small angles, very few reflected back
3

Electronic Configuration and Bohr-Bury Rules

  • Electrons are arranged in shells K, L, M, N corresponding to n = 1, 2, 3, 4
  • Maximum electrons in shell = 2n² where n is shell number
  • K shell (n=1): maximum 2 electrons, L shell (n=2): maximum 8 electrons, M shell (n=3): maximum 18 electrons
4

Atomic Number, Mass Number, and Isotopes

  • Atomic number (Z) = Number of protons in nucleus = Number of electrons in neutral atom
  • Mass number (A) = Number of protons + Number of neutrons = Z + N
  • Standard notation: ᴬZ X where A is mass number, Z is atomic number, X is element symbol

Key Concepts

Atoms contain three types of particlesJBased on alpha particle scattering experimentsNiels Bohr proposed that electrons moveElectrons are arranged in shells following

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Frequently Asked Questions

What are the important topics in What is inside the atom for Telangana Board Class 9 Physical Science?
Key topics in What is inside the atom include Discovery of Sub-atomic Particles, Atomic Models - Evolution of Understanding, Electronic Configuration and Bohr-Bury Rules, Atomic Number, Mass Number, and Isotopes. Study these first, then practise questions on each for Class 9 exams.
How should I revise What is inside the atom for Class 9 exams?
Learn the core ideas first, then work through the 45 practice questions on What is 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.

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