It also tells us that chlorine has 18 neutrons (35 - 17) and, as the number of electrons and protons are equal in a neutral atom ... isotopes are forms of an element that have the same number ...

Everyone at that time imagined the atom as a "plum pudding ... emitted by the radioactive element radium) at a sheet of gold foil only 1/3000 of an inch thick, and tracing the particles' paths.

Players read questions about energy levels and score points by picking the correct element as ... This energy level model shows two electrons on the first energy level and six electrons on the second ...

He showed that every radioactive element decreases in radioactivity ... He discovered the atomic nucleus and developed a model of the atom that was similar to the solar system.