Atomists is the term given to the philosophers over time who believed in the theory and school of though the of the Ancient Greek philosophers Leucippus and Democritus
Our understanding of the atom and nucleus and electrons that surrounds it has come a long way since Ancient Greek times to our understanding of today. With this understanding there have been big leaps in technology and theories that have disproved other theories leading to the model we have today.
The modern Atomic Model was first developed by two key scientists Lavoisier and Dalton with the help of others. They formulated the key concepts of the law of conservation of mass and the existence of atoms as the building blocks of all matter using their knowledge of chemical reactions.