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400 BCE
Democritus
Democritus was the first scientist to make the idea of an atom, a small and unbreakable particle, naked to the human eye, that makes up other substances. -
300 BCE
Aristotle
In the Atomic Theory, it was made out that he didn't believe in it, he believed that all substances were made from either air, fire, water, or earth, and he went out and taught his beliefs. -
Solid Sphere
The solid sphere was put forth by John Dalton in the early 1800s, suggested that since the atoms are indivisible, solid, and spherical particles that combine in fixed ratios to form compounds. -
Aristole was proven wrong
Aristotle's thoughts were later proven wrong, mainly in physics and biology, as new scientific discoveries, like those from Newton, Galile, and Darwin, said the opposite from his theories. -
John Dalton
He suggested the Atomic Theory, with four components, that states all matter is made up of atoms. With that being siad, atoms of the same element are the same, atoms of different elements are different, and atoms combine together to form substances. He put forth a model of an atom, similar to a marble. -
Cathode Ray Tube Experiment
This was conducted by J.J. Thomson in 1897, demonstrated that cathode rays were made of negatively charged particles. Soon was identified as electrons, and it showed that atoms contain subatomic particles. -
Plum Pudding Model
This model was proposed by J.J. Thomson in 1904, stated that atoms are composed of a "pudding". Stating that the pudding is a positive charge with negatively charged electrons embedded like "plums" inside. -
Einstein
He was a theoretical physicist and he was very well known for making the theory of relativity, especially his famous equation, E=mc², which describes the relationship between energy and mass. He also made important contributions to quantum theory. -
Ernest Rutherford
Rutherford conducted the gold foil experiment in which he tried to pass particles through gold foil. When most of the particles went through, a couple did not. He found out that atoms are mostly made up of empty space with positive and small nucleus core. -
Gold Foil Experiment
This experiment was conducted by Ernest Rutherford in 1909. It had showed that atoms have a dense and small nucleus by looking at the most alpha particles passed through gold foil, but some were deflected at large angles. -
Nuclear Model
He proposed by Ernest Rutherford in 1911, he says that an atom has a small, dense nucleus containing positive charge, with electrons orbiting around it. -
Planetary Model
This Model was put forward by Niels Bohr in 1913, he thought that the electrons orbit the nucleus in fixed, quantized paths, similar to planets orbiting the sun. -
Niels Bohr
Bohr found a way to improve the atomic model. He did this by discovering that instead of being pulled into the nucleus electrons travel in different energy levels. -
Schrodinger
Erwin Austrian physicist who developed the Schrodinger equation in 1926, a main role of quantum mechanics that explains how the quantum state of a system evolves over time. -
Heisenberg
Heisenberg was commonly known for his Uncertainty Principle. It talks about how it is impossible to at the same time know both the exact position and momentum of an particle. -
J.J. Thomson
Thomson used cathode rays. He found that the electron measures the bending of rays and began to be used to determine a charge to mass ratio. Further down his distovery, he found the proton, and created a new atomic model, which is commonly known as the "plum pudding" model. -
Quantum Model
This model shows that matter and energy at the smallest scales, where the particles such as electrons behave like both particles and waves. It relies on principles like uncertainty and superposition, challenging classical physics.