Build an atom

Build the first 20 elements, from hydrogen to calcium. Add particles to the nucleus and electrons to K, L, M, and N shells. Connect atomic number, mass number, and outer-shell electrons to an element’s place in the periodic table.

You will get a feel for

1. Discover why the proton count determines the element.
2. Distinguish isotopes from ions by changing neutrons and electrons.
3. Connect electron shells and valence electrons to periods and groups.