The Development of the Modern Atomic Theory
1926
The Schrodinger model of an atom showing that electrons posses wave movement rather than orbiting
Erwin Schrodinger, an Austrian scientist proposed that electrons move like a wave. Theorizing electron movement by studying the model of and atom, he postulated that electrons move in a wave, creating the Schrodinger Equation. This upended the previous idea of particle jumps
c.410 BCE
1902-1903
The gold foil experiment showing radioactive particles(red) bouncing and going through gold foil
The Atomos, what Democritus described as the smallest partcle of matter
Ernst Rutherford(1871-1937), a British-New Zealand scientist, pioneered Radioactivity research. By using Uranium next to thin foils, he was able to determine that one type of radioactivity went through the thin foil and the other didn't. He named these radiation types Alpha and Beta. He used his interest in alpha particles, later to be found as helium particles, to discover that some particles can bounce up to 90 degrees while most go through the gold. Using this, he determined that atoms were made of mostly empty space. Rutherford won the Nobel Prize in 1908 for his work in Radioactivity.
Democritus(460-370 BCE), a Greek Philosopher, proposes that all things are made up of tiny, un-splittable building blocks in one of his writings. While no experiments were made, he created the foundations for Atomism, the philosophical belief that all matter is made of small particles known as atoms. While he is credited for this, some speculate his teacher, Leucippus founded atomism, although many Pre-Socratic era philosophers even deny Leucippus's existence.
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460 BCE
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c. 1803
1894
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Thomson's plum pudding model consisted of an atom with positive and negative charges scattered around
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1932
Polonium ejecting protons out of wax. This was the method Chadwick used to discover the neutron
As you can see, different elements have different masses as shown by the mass in the element
Au
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Joseph John Thomson(1856-1940) was a British scientist. By studying cathode rays, light rays that follow electric charges, he was able to determine that the electric charge to the mass of the particles was always the same no matter the type of gas, meaning that the particles that made up the gas was universal. He determined with this work that atoms were made of much smaller particles now known as electrons. With this he created the plum pudding model
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John Dalton(1766-1844) was a british scientist who pioneered modern atomic theory. He claimed and theorized that atoms vary in mass and size. While it is unclear as to how he had developed this theory, we know that he used other atomist ideas to develop it.
James Chadwick(1891 – 1974) was a British scientist. He proved the existence of the neutron. At the time, people thought that the nucleus was made of protons and electrons. However, by using polonium to eject protons out of wax, he discovered a neutral particle with similar mass to a proton. He had just discovered the nucleus. In 1935, Chadwick won the nobel prize for his work.
Sources:
(1) Mark, J.; Mark, J. Democritus. https://www.ancient.eu/Democritus/ (accessed Sep 3, 2020).
(2) Niels Bohr | Biography, Education, Accomplishments, & Facts. https://www.britannica.com/biography/Niels-Bohr (accessed Sep 3, 2020).
(3) J.J. Thomson. https://www.biography.com/scientist/jj-thomson (accessed Sep 3, 2020).
(4) Ernest Rutherford | Accomplishments, Atomic Theory, & Facts. https://www.britannica.com/biography/Ernest-Rutherford (accessed Sep 4, 2020).
(5) John Dalton | Biography, Discoveries, Atomic Model, & Facts. https://www.britannica.com/biography/John-Dalton (accessed Sep 4, 2020).
(6) Scientists, T.; Scientists, L. James Chadwick - Biography, Facts and Pictures. https://www.famousscientists.org/james-chadwick/ (accessed Sep 4, 2020).
(7) Erwin Schrodinger | Biography, Discoveries, & Facts. https://www.britannica.com/biography/Erwin-Schrodinger (accessed Sep 4, 2020).
1913
Bohr's Atomic Model
Niels Bohr (1885-1962) was a Danish Scientist that created the Bohr atomic model, the most widely known and accepted model. He created this model after Ernst Rutherford discovered that Atoms were made of a positive nucleus with electrons circling around it. With his model, he said that electrons could only orbit at a specific orbit and that electromagnetic ratdiotion only occurs when electrons jump down an orbit. With his work, he won the Nobel Prize in 1922.
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