Democritus was the first philosopher to have the idea that * a. atoms have three parts. b. all atoms of the same element are the same. c. matter is made of tiny, indivisible particles called atoms. d. atoms participate in chemical reactions.

The answer is; C

However, the theory that atoms are indestructible has been challenged since the discovery of radioactivity. It was realized that atoms can be split into subatomic particles (such as protons, neutrons and electrons). Atoms are only indestructible in chemical reaction since they react in  whole number ratios.