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340
What Aristotle thought the atom looked like.
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340
Aristotle
(384 BC-322 BC) Around 340 BCE Aristotle describes his theory that there are only 5 elements: air, earth, water, fire, and aether. He believed that air was light, earth was cool and heavy, water was wet, fire was hot, and aether was what the stars and planets are made up of. Aristotle believed that the first four elements could be combined to create everything except the stars and planets. He came up with the general idea of elements, but his specifics were wrong. -
460
Democritus
(460 bc-370 bc) Democritus: Democritus believed in his mentor’s atomic theory, “The universe is composed of two elements: the atoms and the void in which they exist and move.” He believed that atoms were tiny bits of matter, and that they couldn’t be destroyed, they’re always moving, they’re invisible, and they differ in some physical traits. His exact theory:
“1.All matter consists of invisible particles called atoms.
2. Atoms are indestructible.
3. Atoms are solid but invisible.
4. Atoms are h -
460
What Democritus thought the atom looked like.
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Antoine Lavoisier
(1743-1794) Antoine Lavoisier: Lavoisier confirmed that water is made up of hydrogen and oxygen, understanding of chemical reactions with air, and enforcement of the Law of Conservation of Mass. He considered 33 things to be elements, which he believed to be a substance that had failed to break down any simpler. -
What Antoine Lavoisier thought the atom looked like.
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John Dalton
(1766-1844) John Dalton: Dalton discovered that that the sum of the total pressure of a mixture of gases is equal to the sum of the individual gases. Dalton’s law mainly only applies to ideal gases not real ones, but he backed up with the explanation that the repelling forces acted between atoms instead of creating pressure. He also had ideas about heating and cooling of gases and how they expaned and compressed. -
What John Dalton thought the atom looked like.
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What Becquerel thought the atom looked like.
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Henri Becquerel
(1852-1908) Henri Becquerel: In February of 1896 he conducted an experiment which began when a uranium-bearing crystal was exposed to sunlight. After being placed onto a photographic plate, the crystal produced its image. Becquerel assumed this was because the absorbed energy from the sun was being released. However, when he returned to the project after a few days of leaving it alone, he discovered that the element had left a strong and clear image even though there was no absorbed energy from -
J.J.Thomson
(1856-1940) J. J. Thomson: Studied the glowing light that follows an electrical discharge in a high-vacuum tube and was able to measure the angle of the rays deflection. This means he could calculate the ratio of the mass of the particles to the ratio of electrical charge. When he found that the type of gas used didn’t have an effect on the experiment he decided that the particles of all gases are the same. Thomson also discovered that atoms are made up of smaller particles (electrons) which dis -
What J.J.Thomson thought thr atom looked like.
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Max Planck
(1858-1947) Max Planck: Revised the idea of how radiation works. Instead of believing that there is one steady flow of energy, he believed that it comes and goes in “discrete packets” (which are later called quanta). -
What Max Planck thought the atom looked like.
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Marie and Pierre Curie
(1867-1934, 1859-1906) Marie and Pierre Curie: Intrigued by Henri Becquerel’s discoveries, she began to test the radioactivity in different substances. Marie used an electrometer to measure the strength of the radiation emitted. She found the sample and using the patterns discovered, Curie began to compare radioactive things together. With the help of her husband she has discovered 2 elements, and won 2 awards. -
What the Curies thought the atom looked like.
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Robert Millikan
(1868-1953) Robert Millikan: Robert Millikan decided to use a detailed scientific procedure to confirm Thomson’s hypothesis. Millikan used a spray bottle to spray water/oil droplets, into a chamber. X-rays were then used to ionize the air (they removed electrons). By intensely studying droplets (that fell slowly in the viewing chamber or rose to the top) he could show that the charge on each drop is a very small but real number. The charge is always a multiple of 1.59*10e-19C. -
How Millikan's experiment worked.
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Ernest Rutherford
(1871-1937) Ernest Rutherford: Realized very early on that there are two types of radiation, which are positively and negatively charged (alpha and beta). He also proved that the radioactivity of each element decreases at its own rate (called a half-life) until it eventually becomes stable. He worked to prove that if you expelled part of an atom at a high velocity you could turn it into another radioactive element. Rutherford also developed a model of the atom that looked like the solar system o -
What Ernest Rutherford thought the atom looked like.
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Niels Bohr
(1885-1962) Niels Bohr: Bohr believed that Ernest Rutherford’s theory that all atoms had a small dense nucleus, which was surrounded by a cloud of very light electrons, was wrong. Bohr knew (and used Max Planck’s work to help) that since physics state that electrons orbiting the nucleus should keep losing energy until they reach the center, there needed to be a model that displayed electrons at certain levels of energy. When an atom absorbed energy, it would rise a level farther from the nucleus -
What Bohr thought the atom looked like.
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Erwin Schrodinger
(1887-1961) Erwin Schrodinger: Schrodinger contradicted the belief of Louis de Brogile by saying that an electron in an atom would move as a wave. Using Bohr’s atomic model and a thesis he had from de Broglie, he calculated the way the electrons moved in wave mechanics rather than particle leaps. -
What Erwin Schrodinger thought an atom looked like.
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Henry Mosely
(1887-1915) Henry Mosely: Mosely used x-ray spectra to study atomic structure more closely, which resulted in a more accurate positioning of elements on the periodic table. (He studied under Rutherford while accomplishing this.) He also published his results from the measurement of the x-ray wavelengths which confirmed the ordering of periodic table by atomic number. When isotopes were discovered, people started to realize atomic mass couldn’t be used as the numbering system anymore, which I why -
Mosely's x-rays
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James Chadwick
(1891-1974) James Chadwick: When James Chadwick’s old mentor, Ernest Rutherford, meets the problem of not knowing what besides protons were adding to the mass of an object, Chadwick files it in his head for future reference. When he repeated the experiments of Frederic and Irene Joliot-Curie he succeeded by being able to determine that the neutron does exist, and that it’s weight is around 0.1 percent larger than the proton. Chadwick ended up publishing his finds in paper, and he eventually rec -
What James Chadwick thought the atom looked like.
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What Werner Heisenberg thought the atom looked like.
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Werner Heisenberg
(1901-1976) Werner Heisenberg: Heisenberg said that electrons do not actually travel in organized orbits, and that all electrons that contain protons will then change physics and momentum (the Uncertainty Principle). Heisenberg used mathematics instead of science to understand an atom’s electrons pattern. He used quantum mechanics which were used to interpret the behavior of particles and atoms.
