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Chapter 12: Atoms

NCERT Class 12 Physics, Part II, Chapter 12. 5 lessons, 12 narrated 3D videos, 5 simulations and 10 quiz questions, following the textbook section by section.

• Alpha scattering and Rutherford’s modelNCERT §12.1–12.2 · 3 narrated 3D videos, 1 interactive simulation and 2 quiz questionsBy 1900 we knew that atoms contain electrons, and that an atom as a whole is neutral. So where is the positive charge, and how is it arranged?
• Atomic spectraNCERT §12.3 · 2 narrated 3D videos, 1 interactive simulation and 2 quiz questionsPass the light from an ordinary bulb through a prism. You get a smooth band of all colours, from red to violet, with no gaps. This is a continuous spectrum. A hot, dense…
• The Bohr model of hydrogenNCERT §12.4 · 3 narrated 3D videos, 1 interactive simulation and 2 quiz questionsRutherford’s planetary atom has a serious problem. An electron going round in a circle is accelerating, towards the centre.
• Line spectra of hydrogenNCERT §12.5 · 2 narrated 3D videos, 1 interactive simulation and 2 quiz questionsIn a discharge tube, collisions knock hydrogen atoms into excited states. The electron then drops back to lower levels, emitting one photon in each jump.
• de Broglie’s explanation of Bohr’s postulateNCERT §12.6 · 2 narrated 3D videos, 1 interactive simulation and 2 quiz questionsBohr’s second postulate says the angular momentum is a whole-number multiple of h over 2π. It works beautifully, but why should nature pick these orbits? Bohr gave no…