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In 460 BC, Democrotis was born. He proposed the theory of perception, that things can’t come from nothing, so there must be tiny invisible things (atoms). Changes in objects are from adding or taking away atoms. “Thin layers of atoms, are constantly sloughed off from the surfaces of macroscopic bodies and carried through the air.” (Stanford) He also notices they clump together based on size.

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Dalton creates the atomic theory. This is the theory that all things are made of atoms and that atoms cannot be created nor destroyed.

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In this year, Mendeleev created the first draft of the periodic table of elements. He got the idea when writing down atomic numbers with their mass and charge. He divided the into columns and made his breakthrough. In 1871, he published the final copy of what we see today as the periodic table. (Chemistry World)

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Ernest discovered the nucleus of the atom. He realized that the nucleus is the place of the atom that has mass. He also assigned the atoms atomic numbers. (Nobel Prize)

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Thomson discovers the electron! After studying positive rays and testing them for most of his career, he discovered in neon that there were two different atoms making it.

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Bohr worked out a picture of the atomic structure while studying the quantum theory, which still fits today.

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While studying papers about specific heats of solids, he created Schrödinger’s wave equation. This was a major contribution to quantum mechanics, since it is a key result.

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Chadwick discovers the neutron! After his work on nuclear sciences, he proved the existence of neutrons.

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After the discovery of the neutron by James Chadwick, Heisenberg made a model of proton and neutron interaction (aka strong force). He also contributed to the quantum field theory.