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John Dalton
Born in Eaglesfield, United Kingdom: September 6, 1766
Died: July 27, 1844 -
Dalton’s atomic theory
Dalton stated that all matter consists of very small particles, called atoms, which are identical in their size and mass as well as their chemical properties. Dalton also theorized that atoms of one given element are different from those of another element. This created a whole new perspective of matter in the known universe and paved the way to all atomic research. Dalton’s proposal could, arguably, be considered one of the most important discoveries in chemistry. -
Albert Einstein’s pollen grain experiment
When an English botanist Robert Brown noticed that pollen seeds suspended in water moved in an irregular "swarming" motion. Einstein reasoned that tiny but visible particles, atoms, were suspended in a liquid, atoms were causing them to jiggle by hitting the pollen grains. This was called Brownian motion. It proved the existence of atoms to the scientific world and would lead to a plethora of discoveries such as Ernest Rutherford’s unearthing of the nucleus. -
Dmitri Mendeleev
Born in Tobolsk, Russia: February 8, 1834
Died: February 2, 1907 -
JJ Thompson
Born in Manchester, United Kingdom: December 18, 1856
Died: August 30, 1940 -
Dmitri Mendeleev’s periodic table
Russian chemist Dmitri Mendeleev transcribed symbols for the known chemical elements, he then put them in order of their atomic mass and created an early elemental table. He invented the ancestor of the periodic table. Mendeleev’s table of the known elements went on to become one of the most important pieces of information in chemistry. It is still known to this day to be one of the greatest inventions the history of chemistry. -
Ernest Rutherford
Born in Spring Grove, New Zealand: August 30, 1871
Died: October 19, 1937 -
Albert Einstein
Born in Ulm, Germany: March 14, 1879
Died: April 18, 1955 -
Neils Bohr
Born in Copenhagen, Denmark: October 7, 1885
Died: November 18, 1962 -
Erwin Schrödinger
Born in Vienna, Austria: August 12, 1887
Died: January 4, 1961 -
Louis de Broglie
Born in Dieppe, France: August 15, 1892
Died: March 19, 1987 -
JJ Thompson discovers the electron
In 1897 JJ Thomson discovered the electron by using cathode rays. He saw that, when they were in a vacuum, their flow pattern could be manipulated by magnets. He determined that cathode rays were negative particles, and he called these electrons. His discovery led to Robert Millikan finding an accurate way to determine the electron’s charge. He received various honors, including the Nobel Prize in Physics in 1906. -
Ernest Rutherford’s experiments
Rutherford discovered the nucleus through his gold foil experiment. During this experiment, he shot positively charged uranium particles through a sheet of gold. The vast majority of these particles travelled directly through the gold, but in occasion a few would be repelled back towards their source. Rutherford concluded that there was a very small positively charged mass in the atom. He called this the nucleus. His discovery assisted James Chadwick in unearthing the neutron. -
Werner Heisenberg
Born in Werzburg, Germany: December 5 1901
Died: February 1 1976 -
Millikan’s oil drop experiment
Robert Millikan performed an experiment during which he calculated the charge carried by an electron. He did this by spritzing oil droplets into a closed space that had electromagnets on the top and bottom. He adjusted the electric input until he could isolate a droplet and make it hover. He then used this data to calculate electric charge. This experiment helped determine the structure of electricity and would lead to an understanding and use of electricity as a power source. -
Neils Bohr’s theory
Bohr suggested that the electrons in every atom could only travel around the nucleus in a specific orbit. He also concluded that light was given off by electrons jumping to lower orbits, which, he believed, expelled energy. This model helped explain why atoms only give off light in certain wavelengths. -
Louis de Broglie’s experiments
In 1924, Louis de Broglie hypothesized that electrons could be described not only as particles, but waves. This stemmed from the observation of electrons reflecting off of crystals and dispersing in different metals. His idea contributed to the development of other ideas like Erwin Schrödinger’s wave equation which explained the allowed energy levels in an orbit. -
Erwin Schrödinger’s wave equation
Formulated “Schrödinger’s wave equation” which determines the energy levels of electrons, or waves, orbiting in an atom. This further supported Louis de Broglie’s that electrons could function as waves. Schrödinger’s equation became an essential part in calculating the energy levels of electrons. It is still a main way to determine energy levels of electrons in the atom to this day. -
Werner Heisenberg’s theory
Heisenberg expounded on Bohr’s electron theory. He formulated mathematical equations that could determine quantum mechanics. He also proposed the uncertainty principle, which stated how the position and velocity of a given particle cannot be calculated together at the same time. This contradicted Bohr’s theory of orbiting electrons and created a firm backing for Heisenberg’s argument which was that electrons can’t have an exact know position or velocity. -
Robert Millikan
Born in Morrison, Illinois: March 22, 1968
Died: December 19, 1953