Explain why a few alpha particles bouncing back suggested that most of the atom's mass is concentrated in the nucleus.

Within The development of the model of the atom, this learning objective asks you to explain why a few alpha particles bouncing back suggested that most of the atom's mass is concentrated in the nucleus. Focus on the approved ideas particles, back, suggested, alpha, bouncing and connect them clearly to Atoms and isotopes. A strong response should state the relevant particle, radiation, isotope, decay, half-life or nuclear-equation idea, then explain how it answers the exact command word. Avoid swapping nearby concepts such as atomic number and mass number, isotope and ion, alpha, beta and gamma radiation, or contamination and irradiation.