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John Dalton
John Dalton was an English school teacher. After writing a book n meteorolgy, he wanted to know more about how it worked, and what water was made of. He theorized that there were things called 'H's and 'O's and that they could go together to make water. He also developed the formula for writing down chemistry. To make his discoveries he realized that certain gases could only be combined in certain proportions, and that this is true if two different cmpounds share the same element as a group. -
J.J. Thomson
Thomson discovered elextrons in 1897. After an early career in computational chemistry, and conducted experiments to study electric discharges in a high-vacuum cathode-ray tube. He interpreted the deflection of the rays by charged magnets and plates as evidence of subatomic particles. He then calculated these as having an immense charge-to-mass ration, and further suggested that the atom was a sphere of positive matter in which electrons are positioned by electrostatic forces. -
Albert Einstein Other Papers
In 1905 Albert Einstein wrote a series of papers that threw him into the tempest of history. The first was about the motion of particles suspended in liquid. He developed a formula that showed the visible motion was due to invisible motion of the molecules in the liquid. The next paper he wrote was about the photoelectric effect, which is the release of electrons from metal when light is shone on it. Although not popularized, it was actually this paper that won him his Nobel Prize. -
Einstein Special Theory of Reletivity
After publishing his first papers of that year, Einstein went on to write his Special Theory of Relativity. This unprecedented paper declared that neither time, weight, or mass are constant. This is because when moving at high speeds, these get compressed, and only the speed of light remains constant. This theory is also where we get his famous equation E=Mc^2. -
Ernest Rutherford
Ernest Rutherford made important discoveries in radioactivity and nuclear physics. He discovered alpha and beta rays, and wrote the laws of radioactive decay. He further recognized alpha particles as helium nuclei, and described the hydrogen nucleus as a proton. However one of his most famous experiments was the gold leaf experiment. He set up a thin sheet of gold and a plate of phosphorous, which flashes with radioactivity. Then he counted the number of alpha particles the got through the gold. -
Ernest Rutherford Continued
Next in his gold leaf experiment, they calculated the number of particles which bounced back off of the gold leaf. He found that about 1 in 8000 alpha particles bounced back off of the gold leaf. Rutherford realized that the particles which bounced back were hitting the nucleas of the gold. His diagram of an atom was similar to the solar system, with orbiting electrons around a nucleus. -
Robert Millikan
Millikan conducted what was to become the famous oil drop experiment. He suspended a miniscule drop of oil between capacitor plates to measure the incremental charge on an electron. He believed that the oil drop would pick up a charge due to friction. When monitoring multiple drops, he was able to compare the time that the drop took in order to fall under gravity alone with the time under applied voltage. Millikan was able to discover the charge, and thus the mass of an electron. -
Neils Bohr
Neils Bohr is most famous for his creation of a popular atomic model. He described the atom as a small, positively charged nucleus surrounded by orbiting electrons. The electrons travel in seperate orbiting levels, and the number of electrons in the valence electron shell helps determine the properties of the element. He also contributed to the understanding of nuclear fission, and quantum mechanics. He was the first to state that electrons can be viewed as either a particle or a wave. -
Einstein General Theory of Relativity
Ten years later, Einstein wrote his general theory of relativity because he was frustatrated at the old theory not being able to express gravity. In this paper, he introduced a concept called space-time, which is the fabric of the universe. Gravity is a bending of space time, which cause things to draw nearer to the object. He staked his reputation on astronomers being able to detect changes in the apparent positions of stars near the sun during a solar eclipse. It was confirmed. -
Erwin Schrodinger
Schrodinger suggested that electron behave like waves, not just particles, and so their exact location in an orbit cannot be calculated. This is called the uncertainty principle. In his model, each electron shell is made up of sub-shells, and the number of sub-shells in a shell is the same as the shell number. There is no limit to the number of shells, only to the size of the nucleus. Each subshell can be divided into orbitals, and each orbital can hold a maximum of two electrons.
