Atomic Structure — Revision Notes
NIOS · Class 10 · Science & Tech
Atomic Structure revision notes for NIOS Class 10 Science & Tech: 4 topics in quick points. Part of the NIOS Class 10 Science & Tech syllabus.
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Key Topics to Revise
1. Discovery of Subatomic Particles
- Dalton's atomic theory was proposed in 1803 and explained the law of conservation of mass, law of constant composition, and law of multiple proportions.
- The theory later failed partially because the electron was discovered, proving that the atom is divisible.
- Sir William Crookes carried out cathode ray tube experiments in 1885.
2. Atomic Models
- Thomson proposed the plum-pudding model of the atom.
- According to Thomson's model, atoms can be considered as a large sphere of uniform positive charge with small negatively charged electrons scattered throughout it.
- The model is also compared to a watermelon, with the pulp as positive charge and the seeds as electrons.
3. Atomic Number, Mass Number, and Electronic Configuration
- Atomic number is the number of protons in an atom and is denoted by Z.
- For a neutral atom, atomic number = number of protons = number of electrons.
- Mass number is the total number of protons and neutrons in the nucleus and is denoted by A.
4. Quick Fact Review for Exams
- Dalton's atomic theory was proposed in 1803.
- J.J. Thomson discovered the electron in 1897.
- Eugen Goldstein discovered anode rays in 1886.
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