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Aristotle Atomic Model
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Aristotle
Aristotle suggested that matter is made of atoms, and that matter will always exist. He discovered that substances were made up of five elements: fire, water, air, earth, and aether, that they had five distinct qualities, and that they would align into their rightful places and be at rest. He also developed methods for gathering scientific facts, which proved as the basis for all scientific work. Aristotle proposed a fifth element, aether, in addition to the four proposed earlier by Empedocles. -
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Democritus
Democritus believed that if you continually cut a substance in half, eventually you would get an uncuttable piece. He called these uncuttable pieces particles. He suggested that atoms were hard and small particles, compiled by one substance, and in one particular shape. He also suggested they were always moving and that they combined with each other. Democritus stated that the universe is made up of empty space and a nearly infinite number or invisible particles differing in arrangement, form, a -
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Democritus Atomic Model
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Antoine Lavoisier
Antoine Lavoisier provided the formula for the conservation of matter in chemical reactions, and also distinguished between an element and a compound. He created the idea of having one single common language for all of science to use. Lavoisier is considered the founder of modern chemistry. He clarified the concept of an element as a simple substance that could not be broken down by any known method of chemical analysis, and he devised a theory of the formation of chemical compounds from element -
Antoine Lavoisier Atomic Model
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John Dalton
John Dalton formed the atomic theory, which states that all matter is composed of indivisible particles called atoms that are all alike and have the same atomic weight for each element. These atoms possess unique characteristics and weight for different elements. He claimed the reason elements combined was because all elements are made up of atoms. He also created a three-part atom theory.
1. All particles are made of atoms; they cannot be divided or destroyed.
2. Atoms of the same elements ar -
John Dalton Atomic Model
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Henri Becquerel
Henri Becquerel discovered natural radioactivity and nuclear energy. He also discovered x-rays by observing the fluorescence they produced. While investigating phosphorescence in uranium salts, Becquerel accidentally discovered radioactivity. He wrapped a fluorescent substance, potassium uranyl sulfate, in photographic plates and black material in preparation for an experiment requiring bright sunlight. However, prior to actually performing the experiment, Becquerel found that the photographic p -
Henri Becquerel Atomic Model
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J.J. Thomson
J.J. Thomson inferred that there are small negatively charged particles inside of every atom. He was also the first person to discover the electron. Thomson also developed the plum-pudding model of the atom, which describes the atom as a positive sphere with small electrons inside. Thomson developed a method for separating different kinds of atoms and molecules by the use of "positive rays”. He thought that the atom looked like plum pudding. This meant that this that the atom was a ball of posi -
J.J. Thomson Atomic Model
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Marie & Pierre Curie
Pierre Curie and his wife Marie Curie stated that radioactive materials cause atoms to break down spontaneously, releasing radiation in the form of energy and subatomic particles. They discovered that the strength of the radiation did not depend on the compound that was being studied. It depended only on the amount of uranium or thorium. They suggested that chemical compounds of the same element generally have very different chemical and physical properties. They suggested that the ability to r -
Max Planck Atomic Model
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Max Planck
Max Planck suggested that radiant energy can only be emitted or absorbed in discrete quantities, like small packages or bundles. He stated that that radiation is quantized and that energy is radiated in small, discrete units, which he called quanta. He gave the name quantum to the smallest quantity of energy that can be emitted or absorbed in the form of electromagnetic radiation. Planck built on previous radiation and energy theories and discovered that energy is quantized within atoms. -
Robert Millikan
Robert Millikan discovered the charge of an electron with his oil drop experiment. To do this, he built a spray used to spray oil droplets. As the droplets came out of the nozzle they would become electrically charged by friction. He would then choose one of the droplets and measure the speed at which it was falling. He would then switch on an electrostatic field, and adjust it until the droplet stopped falling. From the speed of falling, he could calculate its weight. After knowing the electric -
Robert Millikan Atomic Model
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Ernest Rutherford
Ernest Rutherford explained natural radioactivity, determined the structure of the atom, and changed one element into another (nitrogen to oxygen) by splitting an atom's nucleus. He also discovered the concept of radioactive half-life and proved that radioactivity involved the transmutation of one chemical element to another. Rutherford also discovered that protons are in the core of an atom, and are not surrounding it like the electrons. He suggested that the atom is mostly empty space. He did -
Ernest Rutherford Atomic Model
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Niels Bohr
Niels Bohr suggested that electrons travel around the nucleus in definite paths. These paths are always at a certain "level" away from the nucleus. He also stated that electrons cannot travel in between each path, but they can jump from one path to another. Niels Bohr discovered that electrons in atoms are arranged according to their energy levels. He also created the Bohr Model, which shows the atom as a small, positively charged nucleus surrounded by electrons that travel in circular orbits ar -
Niels Bohr Atomic Model
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Henry Moseley
Henry Moseley found that atoms of each element contain a unique positive charge in their nucleus. This discovery showed that an atom's identity comes from the number of protons in its nucleus. Using x-ray tubes, he determined the charges on the nuclei of most atoms. He discovered that the atomic number of an element is equal to the number of protons in the nucleus. This was used to reorganize the periodic table based upon atomic number instead of atomic mass. Mosely elaborated and proved Rutherf -
Henry Moseley Atomic Model
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Erwin Schrodinger
Erwin Schrodinger discovered the electron cloud model theory. He wrote a number of fundamental results in the field of quantum theory, which formed the basis of wave mechanics. He also formulated the wave equation. He created an original interpretation of the physical meaning of the wave function. Schrodinger contributed to the development of quantum wave mechanics. He also created a mathematical formula used in quantum mechanics. He discovered the equation that can be used to determine the prob -
Erwin Schrodinger Atomic Model
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Werner Heisenberg Atomic Model
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Werner Heisenberg
Werner Heisenberg suggested that it was impossible to measure the velocity and position of an electron at the same time. He is known for his Uncertainty Principle, which states that the exact location and energy of an electron cannot be determined simultaneously. Finding one value means that there will be some uncertainty when finding the other value. The principle states that you can measure a quantum particle's location or speed, but not both accurately.
If you try to accurately measure its -
James Chadwick Atomic Model
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James Chadwick
James Chadwick discovered the neutron and found that they are located inside of the nucleus. It was known as the neutron because of its lack of electric charge. He suggested that unlike positively charged alpha particles, which are repelled by the electrical forces present in the nuclei of other atoms, neutrons do not need to overcome any Coulomb barrier and can therefore penetrate and split the nuclei of even the heaviest elements. Chadwick built on everybody else's ideas about the nucleus and
