History of the Atomic Model
Published on Nov 20, 2015
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Democritus (460 b.c.–370 b.c.)
The first person to think about the fact that there had to be something that made up everything was Ancient Greek philosopher Democritus. He reasoned that atoms made up everything and were both indivisible and indestructible by nature. He also stated that nothing exists in them except empty space. Most of his theories will come to be proven false.
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John Dalton (1766-1844)
John Dalton was the beginning of the modern exploration and identification of atoms, more than 2000 years after Democritus. An English chemist and a school, teacher, John conducted experiments on his own, and formed a hypothesis about the behavior of atoms. Some of his ideas are listed below:
All elements are composed of tiny indestructible particles called atoms
Atoms of the same element are identical to each other, and only each other
Atoms of different elements can mix together in simple whole number ratios to form com…
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J.J. Thomson (1856–1940)
J.J. Thomson was an English physicist who did an experiment that involved passing electricity through a gasses in a cathode at very low pressure. He discovered that the particles were attracted by one end while repelled at the other. Knowing about the fact that these are negative and positive attributes, he hypothesized that atoms have electrons on them
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Robert A. Millikan (1868–1953)
Robert Millikan was a U.S. Physicist who carried out experiments to find an electrons charge. Using data from his experiments he was able to calculate the charge and the mass of electrons. His work was pretty accurate considering his time period, with him discovering that an electron has one unit of negative charge and has a mass of 1/1840 the mass of hydrogen
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Eugen Goldstein (1850–1930)
Eugene was a scientist who observed a cathode ray and observed rays traveling opposite the cathode rays, and concluded that they we're composed of positive particles
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Ruthford (1911)
Ruthford was a scientist at the University of Manchester, and he and his co-workers conducted an experiment using alpha particles and a thin sheet of gold foil. His results concluded that atoms were in fact hollow, but had a few patches spots where there were things floating around. From all this he proposed a new atomic model
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Niels Bohr (1913)
Niels Bohr was a student of Ruthford's who took the development of the atomic model even further. He took all the recent discoveries of the atom and proposed an even newer atomic model. He also proposed that the electrons were locked in orbit at specific levels, and that certain energy levels are needed to go from one level to the next.
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James Chadwick (1891–1974)
James was an English physicist who discovered another particle called the neutron. This atom is not charged positively or negatively. They are extremely small and scientists believe they are composed of even smallest particles called quarks.
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Erwin Schrödinger (1926)
Erwin was an Austrian physicist who created an equation that predicts where electrons will be. He also made the quantum mechanical model.
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