{"id":2258,"date":"2023-05-02T08:03:25","date_gmt":"2023-05-02T08:03:25","guid":{"rendered":"https:\/\/vartmaaninstitutesirsa.com\/?page_id=2258"},"modified":"2024-03-14T15:13:13","modified_gmt":"2024-03-14T15:13:13","slug":"chapter-12-atoms","status":"publish","type":"page","link":"https:\/\/vartmaaninstitutesirsa.com\/index.php\/chapter-12-atoms\/","title":{"rendered":"Chapter 12 Atoms"},"content":{"rendered":"

Unit VIII: Atoms and Nuclei\u00a0<\/span><\/strong><\/h1>\n

Chapter 12 Atoms<\/h3>\n

Chapter\u201312: Atoms : <\/span><\/strong>Alpha-particle scattering experiment; Rutherford’s model of atom; Bohr <\/span><\/strong>model of hydrogen atom, Expression for radius of nth possible orbit, velocity <\/span><\/strong>and energy of electron in nth orbit, hydrogen line spectra (qualitative <\/span><\/strong>treatment only).<\/span><\/strong><\/p>\n

\n

\"J.J1 J J Thomson’s Model of an Atom:<\/span><\/u><\/strong><\/p>\n

According to JJ Thomson model of an atom, an atom is just like a watermelon in which seeds behave as electrons and reddish parts behave as\u00a0<\/span>\"\"\u00a0charged matter. Atom as a whole is electrically neutral.<\/span><\/p>\n

Failure of JJ Thomson Model:<\/span><\/u><\/strong><\/p>\n

\uf0d8<\/span>It could not explain the origin of spectral series of hydrogen atom.<\/span><\/em><\/p>\n

\uf0d8<\/span>It fails to explain the large angle scattering of hydrogen atom.<\/span><\/em><\/p>\n

2 Rutherford \u03b1-particle Scattering Experiment\u00a0<\/span><\/u><\/strong>imp<\/sup><\/span><\/u><\/strong>:<\/span><\/u><\/strong><\/p>\n

Rutherford along with Geiger and Marsden performed a number of experiments on the scattering of \u03b1-particle due to atoms of thin gold foils. The experimental demonstration of their model is as below.<\/span><\/p>\n

\"\"Experimental Setup:<\/span><\/u><\/strong><\/p>\n

A narrow beam of \u03b1 particle obtained from a radioactive substance placed in a lead cavity is generated, which is allowed to fall on a thin gold foil, after passing through a narrow slit. After striking the gold foil, the beam is allowed to fall on Z<\/span>\"\"\u00a0screen and the pattern is seem with the help of movable detector. As shown in fig.<\/span><\/p>\n

Observation:<\/span><\/u><\/strong><\/p>\n

Rutherford observed that<\/span><\/p>\n