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What is inside the atom

Kerala Board · Class 9 · Science

Quick revision notes for What is inside the atom — Kerala Board Class 9 Science. Key concepts, formulas, and definitions for last-minute revision.

45 questions24 flashcards5 concepts

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Key Topics to Revise

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

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Full Notes

Key Concepts

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

Frequently Asked Questions

What are the important topics in What is inside the atom for Kerala Board Class 9 Science?
What is inside the atom covers several key topics that are frequently asked in Kerala Board 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 What is inside the atom — Kerala Board Class 9 Science?
Understand the core concepts first, then work through the 45 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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