Question

which statement best supports thomsons idea that atoms contain negatively charged particles? electrical and magnetic fields deflect cathode rays in mathematically predictable ways. the masses of substances before a reaction equal the masses of substances after a reaction. alpha particles passing through a thin sheet of gold foil are scattered in all directions. all atoms of a given element are identical, but they differ from atoms of other elements.

Explanation:

Thomson discovered electrons (negatively - charged particles) through cathode - ray experiments. Electrical and magnetic fields deflecting cathode rays in predictable ways shows that cathode rays are made of charged particles, supporting Thomson's idea. The second option is related to conservation of mass, the third to Rutherford's gold - foil experiment, and the fourth to Dalton's atomic theory.

Answer:

Electrical and magnetic fields deflect cathode rays in mathematically predictable ways.