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350
Aristotle
Aristotle (350 B.C.) disagreed with Democritus' model. He felt that there was no smallest part of matter and that different substances were made of earth, fire, air, and water. Aristotle did not have an atomic model due to the fact that he thought atoms did not exist. -
400
Democritus
Democritus was the first scientist to create a model of the atom. He was the first one to discover that all matter is made up of invisible particles called atoms. He created the name "atom", which means uncuttable. He also discovered that atoms are solid and indestructable. His model was just a round solid ball, because that's all he knew -
Period: 400 to
Atom Timeline
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Antonie
Antonie Lavosier was the man that founded several elements and put the first table of elements together. He used Aristotle's ideas to create experiments invesigating combustion and oxidation. He also found important elements like oxygen, hydrogen, and sulfur. He discovered that water was made of oxygen and hydrogen, and air included nitrogen. Lavoisier also created the first chemistry textbooks and tables. -
John Dalton
An English chemist who first created the Atomic Theory of Matter, which is a compilation of Democritus' findings and Dalton's own findings. He included in this theory that all matter is made of atoms, that atoms cannot be created nor destroyed and also, atoms of different elements combine in whole ratios to form chemical compunds. His theory would later contribute to an advance in the atomic model. -
Henri Becquerel
Henri Becquerel was born into a family scientists. With influences of his father and grandfather, Bequerel worked with properties of the atom, such as magnetism and radioactivity. His biggest achievements were in the field of radioactivity. In his earlier works, Bequerel worked with light and the absorption of light by crystals. He also looked at the mechanics of X-rays. His discovery of radioactivity allowed later scientists to perfect the atomic model. -
J.J. Thomson
J.J. Thomson was a very important scientist when it came to the atomic model. Up until his time, all models of the atom looked like a big solild ball. J.J. Thomson discovered the electron, which led him to create the "plum pudding" atomic model. In this model, he thought that the atom was mostly positive, and negative electrons wandered around the atom. The "plum pudding" model influenced other scientists to create other models -
Madame Curie
Marie "Madame" Cuie was contributed atomic chemistry by exploring the mysteries of radioactivity. After radiation was discovered by Henri Baquerel, Marie decided to look further into this discovery. Through this she discovered the elements radium and polonium and won the Nobel Peace Prize for her works in radioactivity. Her discovery later added to the atomic model. -
Max Planck
Max Planck was a German scientist that created the Quantum Theory. In this theory, Planck stated that energy was given off in little packets of energy. These were called photons when talking about light. He discovered that the energy in wave form is restricted to specific quantaties. This discovery led to the understanding of energy levels in atoms, since quantums are leaps in the atom. -
Ernest Rutherford
Ernest Rutherford was another scientist that changed the atomic model. He felt that Thomson's model was incorrect, so he created a new one. He created the nucleus, and said that instead of the positive matter being the whole atom, it was just in the middle. He said the atom was mostly empty space and that the electrons surrounded the positive nucleus. -
Niels Bohr
Niels Bohr was a Danish scientist. He was a student of Rutherford. He decided to make a new model based off of Rutherford's model, but changed the orbit of the electron. Also, he created energy levels in the atom, where only a certain amount of electrons could fit on one energy level of the atom. Bohr also used Planck's ideas in order to create quantum mechanics, his new concept regarding energy. This model is still used to this day.
