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He proposed that all matter consisted of four elements including Earth, Air, Water and Fire. There were also four qualities including dryness, hotness, coldness, and moistness.
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He brought up the idea of atom. He proposed that matter was composed of tiny particles, atoms. They join with other atoms to create more atoms.
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First people to test the theories that had emerged about the existence of atoms and the different elements. Before the age of the Alchemists, the concept of atomic theory was just a bunch of ideas.
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One of the first greeks to develop the theory of the atom, which was formalized and elaborated on by his pupil Democritus
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Proposed a universe with small solid masses in motion.
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He introduced the theory that contained the first clear statement of the law of conservation of electric charge.
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He was the one to formulate the law of conservation of mass, which states that the total mass in a chemical reaction remains constant.
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He proposed that all matter is made of atoms and they are indivisible and indestructible, all atoms of a given element are identical in mass and properties, compounds are formed by a combination of two or more different kinds of atoms, and a chemical reaction is a rearrangement of atoms.
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His atomic model
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He published his law of definite proportions in 1794 (accepted in 1812).
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He suggested that the structure of atoms was related to electricity in someway. He developed laws of electrolysis.
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Built the first Cathode Ray Tube
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He created the first formal periodic table of element with the 56 elements that were known during his time.
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He discovered radioactivity and was able to isolate radium and polonium.
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He did cathode ray experiment and discovered the negatively charged particle, electron.
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He did gold foil experiment and discovered the center of the atom, nucleus.
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By studying the decay process of Uranium and Thorium, she discovered radium and polonium and invented the term ‘radioactivity’.
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Gold foil experiment
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He used the idea of quanta (discrete units of energy) to explain hot glowing matter.
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Studied the then new concept of radioactivity. He achieved the separation of uranium from uranium-x. He then observed the gradual decay of the product.
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Published a paper that proved beyond doubt the existence of atoms using the movement of pollen particles in still water, etc.
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Produced device that made a noise when hit with alpha particles
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He did oil drop experiment and determined the charge (e=1.602 x 10 -19 coulomb) and the mass (m = 9.11 x 10 -28 grams) of an electron.
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oil drop experiment
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He developed the Bohr atomic model, with electrons travelling in orbits around the nucleus, and chemical properties being determined by how many electrons are in the outer orbits. He also integrated the Planck quantum theory, stating that when electrons change orbits, they emit a quantum of discrete energy.
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discovered a systematic mathematical relationship between the wavelengths of the X-rays produced and the atomic numbers of the metals that were used
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He introduced (as his doctoral thesis) his theory of particle-wave duality. This theory suggests that particles can behave like waves, and that waves can behave like particles.
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He made the modern accepted model of the atom, with orbitals rather than the shells/energy levels that Bohr described.
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He introduced the uncertainty principle. A principle which states that the speed and location of an electron cannot be determined simultaneously.
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He established that atomic number is determined by the numbers of protons in an atom.
He also discovered the fourth subatomic particle,the neutron.
