Build an atom simulation


Build an atom from scratch, using protons, neutrons, and electrons. Test different combinations to produce ions and unstable elements.


This resource has been provided by, or developed in partnership with, PhET Interactive Simulations, University of Colorado Boulder

Build an atom simulation, developed by PhET, University of Colorado Boulder. Choose one of two modes, or choose a challenge in the Game section. Click the PhET logo in the resource for more information.


PhET sims are fun, interactive, research-based simulations of physical phenomena developed by the PhET™ project at the University of Colorado. Conversion to HTML5 and tablet compatibility supported by the Royal Society of Chemistry.

Sample Learning Goals:

  • Use the number of protons, neutrons, and electrons to draw a model of the atom, identify the element, and determine the mass and charge.
  • Predict how addition or subtraction of a proton, neutron, or electron will change the element, the charge, and the mass.
  • Use the element name, mass, and charge to determine the number of protons, neutrons, and electrons.
  • Define proton, neutron, electron, atom, and ion.
  • Generate an isotopic symbol for an atom, given the number of protons, neutrons, and electrons.