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450 BCE
Democritus
First discovered the term "atom" after the idea of cutting an apple into smaller and smaller pieces until it couldn't be cut anymore. Due to the influence of Aristotle, the idea of the atom was forgotten about for a really long time. -
Dalton
John Dalton rediscovers the atom. He studied the pressure of gases and the properties of compounds. This made way for Daltons Atom Theory. All substances are made of atoms. All atoms of the same element are alike and have the same mass. Atoms join together to form compounds. He believed that atoms were solid and modeled them out of wood. His models turned out to be too simple/ not detailed enough. -
Thomson
J.J. Thomson discovered electrons. He discovered them through his Vacuum Tube Experiment in which he noticed negatively charged particles. His experiments also showed that the electrons were all alike and smaller than the atom. He then created the Plum Pudding Model to display his findings. -
Rutherford
Ernest Rutherford discovered the nucleus. He discovered it using his gold foil experiments. In the experiment, he shot alpha particles at some gold foil covering a material that would glow when touched by them. Most of the particles passed through. He concluded that atoms were mostly empty space. The ones that didn't pass gave him the conclusion of the nucleus. He then created an atomic model that was more precise than Thomson's. His model had the charges inside the nucleus. -
Bohr
Niels Bohr created the most accurate model of the atom. His model was similar to Rutherford's. His model shows the physical and chemical properties of the elements. His model even shows how the atom works.
