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THe Big ining
John Dalton 1803 Dalton’s breakthrough was in 1803 when he announced the relative weights of atoms based on his experimentation of mixing gasses. His experiments showed that all matter was made up of atoms and that the only difference was their weight. He also created symbols to represent different atoms so they could be experimented with. This essentially started what would become known as atomic theory. Sources: E-learning biographies
http://www.brooklyn.cuny.edu/bc/ahp/FonF/Dalton.html -
J.J. Thompson
J.J. Thompson 1904 In 1904 Thomson created a model of the atom that influenced many other scientists.
The model showed that that atom was positive matter and that the electrons in the atom were held together by electrostatic forces. His interest in trying to estimate how many electrons were in an atom based on measuring how light scattered in atoms put his student Ernest Rutherford on the right track in Rutherford’s important research. Sources:
Chemical Heritage Foundation http://www.chemhe -
Robert Millikan
Robert Millikan 1909 Millikan was known for his oil drop experiment in 1909, which allowed for the measurement of the electron’s charge. The experiment was the first time anyone had tried to detect and measure a subatomic particle’s effect. Millikan used an atomizer to spray oil and let the droplets fall into a basin that had a microscope attached, which he used to measure the velocity and from there he could measure the mass of each drop. He then used a battery to irradiate and charge the dro -
Ernest Rutherford
1911 In 1911, Ernest Rutherford made a big contribution to the understanding of the structure of the atom with his publication of his atomic theory. This said the atom had a central positive nucleus and was surrounded by negative oribiting electrons. This was a breakthrough because it theorized that the main mass of the atom was in the tiny nucleus and that the rest of the atom was pretty much empty space. The main experiment Rutherford used was called the Gold Foil experime -
Niels Bohr
Niels Bohr 1913 Bohr’s big contribution was in 1913 when he applied quantum theory to Ernest Rutherford’s atomic structure. Bohr figured out from Rutherford that electrons travel in stationary orbits and this allowed him to make calculations of the possible energy levels of the orbits and theorize that the emission of light happens when an electron moves into a lower energy orbit. He developed a diagram showing how the outer orbits have more electrons than inner orbits. And Bohr also figured -
Arnold Sommerfield
Arnold Sommerfield 1911-1916 Sommerfield had two big contributions that came about between 1911 and 1916.
After 1911, he focused on quantum theory, or looking at how atoms and sub atomic particles work. In researching this he replaced Bohr’s idea of circular orbits of electrons with the idea that they also moved in an elliptical way. Then in 1916 he invented the magnetic quantum number, and later the inner quantum number to help explain this and help scientists know more about the workings o -
Irving Langmuir
Irving Langmuir 1919 In 1919 Langmuir came up with the concentric theory of atomic structure.
Langmuir’s theory looked at specific details of chemical forces happening where different substances come together. He won the Nobel Prize in 1932 for this theory. He is also known for his atomic structure work before 1919. In 1915 he came figured out how many electorn pairs an atom can share with other atoms. Source: NNDB Tracking the Entire World http://www.nndb.com/people/776/000079539/ -
Otto Stern and Walther Gerlach
Otto Stern and Walther Gerlach 1920 The Stern-Gerlach experiment in 1920 showed the existence of the electron spin two years before the theory was written up. Sterns and Gerlach boiled silver and got the atoms from it and created a beam of those atoms using flat photographic plates.
But instead of getting one beam they got two, meaning they split or created a spin. Source: http://library.thinkquest.org/19662/high/eng/exp-stern-gerlach.html -
Erwin Schrodinger
Erwin Schrodinger - 1926 Schrodinger in 1926 added to the Bohr model of the atom by using math to show how you could estimate where an electron might be at any time in an atom.
The model has the nucleus of the atom appear like an electron cloud. In the dense area of the cloud, it is more likely the electron will appear and if it is less dense, the electron is probably not there. Findings conclusions made re: structure of atom This model led to the notion that there were different energy le -
James Chadwick
James Chadwick 1932 Chadwick’s contribution was in 1932 when he discovered that neutrons exist.
Chadwick was able to show that neutrons do exist and that they did not have any electrical charge. This allowed them to penetrate and split the nuclei of atoms because they did not have to get through an electric boundary. This discovery led to the fission of uranium 235, and later the building of the atom bomb. He won the Nobel Prize in 1935 for this. Sources: NobelPrize.org
http://www.nobelprize -
Linus Pauling
Linus Pauling 1939 Pauling’s contribution was the publication of The Nature of the Chemical Bond and the Structure of Molecules and Crystals in 1939. This work contained his resonance theory, which showed that “some molecules ‘resonate’ between different structures, rather than holding a single fixed structure.” This insight made possible the creation of many of the drugs, dyes, plastics and synthetic fibers we take for granted today. Pauling publicized his findings in a series of papers cul -
Murray Gell-Mann and George Zweig
Murray Gell-Mann and George Zweig 1964 Gell-Mann and Zweig came up with the quark theory in 1964, when physicists were beginning to need another explanation for the makeup of the atom. Atoms could no longer be viewed as just protons, neutrons and electrons because a lot of other new particles kept getting discovered. They speculated that some of these new particles were known as quarks, which were kind of building blocks for protons and other subatomic particles. At first he identified three,
