Rutherford scattering – alpha particles, the nucleus and the Thomson model

ChemistryAtomic Structure & Periodic TableAges 15–16

Fire a beam of alpha particles at an atomic nucleus and follow the paths curved by Coulomb repulsion: most particles go straight through, some are deflected through large angles and very rarely one bounces straight back. Switch to the Thomson model (positive charge spread evenly) to see that almost no particle is deflected much — contrary to the experiment. An "aimed" particle with an impact parameter b of your choice lets you compare the simulated deflection angle with the formula tan(θ/2) = k·q1·q2/(2·E·b), and a multi-nucleus mode models the gold foil. Based on the "Rutherford Scattering" simulation by PhET Interactive Simulations, University of Colorado Boulder (CC BY 4.0); rewritten.

Lesson: Atomic structure – the nuclear model of the atom