Question

most of the mass of the atom is concentrated in a very small, dense central area, later called the nucleus, which is about 1/100,000 the diameter of the atom. this was proposed as a result of what data?

Explanation:

Rutherford's gold - foil experiment involved firing alpha particles at a thin gold foil. Most alpha particles passed through (suggesting most of the atom is empty space), but a small number were deflected at large angles or even back. This indicated a small, dense, positively charged nucleus (where most of the atom's mass is concentrated) as the cause of such deflections.

Answer:

Rutherford's gold - foil experiment data.