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Subatomic Particles

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Estimated time: 6 minutes
Maharashtra State Board: Class 12

Key Points: Subatomic Particles

Atoms are made up of three fundamental subatomic particles — electron, proton, and neutron. Their discovery was a milestone in understanding atomic structure.

Discovery Timeline:

Particle Year Scientist Experiment
Electron 1897 J.J. Thomson Cathode ray tube experiment — cathode rays are streams of tiny, negatively charged particles
Proton 1911 Ernest Rutherford Alpha-particle scattering on gold foil — hydrogen nucleus identified and renamed proton
Neutron 1932 James Chadwick Nuclear reaction: bombardment of beryllium with alpha-particles produced neutral, massive particles

Properties of Subatomic Particles

Particle Symbol Absolute Charge (C) Relative Charge Mass (kg) Mass (u) Approx. Mass (u)
Electron e⁻ −1.6022 × 10⁻¹⁹ −1 9.10938 × 10⁻³¹ 0.00054 0
Proton p+ +1.6022 × 10⁻¹⁹ +1 1.6726 × 10⁻²⁷ 1.00727 1 u
Neutron no 0 0 1.67493 × 10⁻²⁷ 1.00867 1 u

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History of atom [00:10:28]
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