According to Aristotle, everything was composed of four elements: earth, air, fire, and water. His ideas prevailed.

Development of the atomic theory of the universe. First one to clearly propose the idea of an atom. (Atomos). He was rejected because he had no evidence to support his claim.

Took science of extraction to a new level, breaking down substances.

They found that certain substances can be broken down even further with chemical reactions. Classified Hydrogen and oxygen as elements.

Dalton's atomic theory was the first complete attempt to describe all matter in terms of atoms and their properties.

Postulated the nuclear structure of the atom, discovered alpha and beta rays, and proposed the laws of radioactive decay.

Nobel Prize in physics for his work on Brownian motion. He settled the cathode ray particle-wave debate by demonstrating that cathode rays carry negative charges and are thus particles.

Thomson discovered the electron and then went on to propose a model for the structure of the atom. His work also led to the invention of the mass spectrograph.

Physicist who discovered the quantum of action now known as Planck's constant

Is known for developing the theory of relativity, but he also made important contributions to the development of the theory of quantum mechanics.

Niels Bohr proposed a theory for the hydrogen atom. Bohr's model explained why atoms only emit light of fixed wavelengths, and later incorporated the theories on light quanta

His theory of quantum mechanics and the applications of it which resulted especially in the discovery of allotropic forms of hydrogen

Co-invented the scanning tunneling microscope (STM), a non-optical instrument that allows the observation of individual atoms in three dimensions.