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330
Alexander the Great- 330 B.C.E.
330BC – Alexander the Great conquers the Persian Empire. -
340
Aristotle
Around 340 B.C.E., Aristotle proclaimed that there were four qualities which created a substance: dry, wet, hot, and cold. For example, water is wet and cold, This went against Democritus' ideas, though people around this time believed this more than Democritus'. -
400
Democritus
Around 400 B.C.E., Democritus thought that all atoms were eternal and unchanging. But he also thought they were different shapes and sizes, and that color depended on the atom (white objects were smooth atoms, blue objects fluid atoms, etc). He coined the term atoms. -
George Washington- 1789
1789 – George Washington becomes first president of the USA. -
Joseph Proust
Proust proposed the Law of Constant Composition (also called the Law of Definite Proportions) in 1799 which claimed that samples of the same chemical compound contain the same elemental composition. -
Library of Congress
1800 – Library of Congress is founded. -
John Dalton
Dalton calculated the different weights of compounds, and said that air was not layered but moved in a constant motion. He talked about fluids expanding under heat and how atoms changed under different conditions. -
California Gold Rush
1848 – California Gold Rush begins. -
Henri Becquerel
In an experiment to see if there was X-ray emission in flourescent light, Becquerel wrapped plates in lightproof paper and shot them with uranium. They blackened. But he observed non-shot uranium, and the same thing had occured. He was the first to talk about radiation. -
Tootsie Rolls
1896 – Leo Hirschfield makes the first Tootsie Roll, named after his daughter. -
Neils Bohr
In 1913, Bohr published his idea that an atom consists of positively charged nucleus is orbited by electrons. He also claimed that electrons travel only in certain orbits, and that inner orbits held fewer electrons that inner ones. -
Max Planck
In 1901 Planck proposed that energy did not flow continuously, but burst out in small pockes called quanta. He is responsible for people starting to think about quantum theory, which influenced Erwin Schrodinger along with many other scientists. -
J.J. Thomson
In 1897, after studying cathode rays, Thomson proposed that they were actually negatively charged particles, and that an atom was not the smallest particle of matter. He created the Plum Pudding Model in 1904 which suggested that the atom contained a positive fluid which balanced the negative electrons. -
1st Radio Broadcast
December 24, 1906 – First audio radio broadcast is made; ships at sea listened to O Holy Night and a Bible passage -
Robert Millikan
In 1909, Millikan conducted the “oil-drop experiment.” This experiment was used to measure the charge of an electron by measuring the electricity in the droplets of an oil mist. -
Ernest Rutherford
Rutherford conducted an experiment in 1911 that determined where alpha rays scattered when they were passed through a piece of thin gold foil. Most barely scattered, but a few spread in different directions, leading him to conclude that the atom contains a positively-charged nucleus surrounded by electrons. -
Louis de Broglie
In 1924, Broglie proposed that electrons moved in waves and patters, similar to that of Max Planck and Einstein. -
Erwin Schrodinger
Erwin Schrodinger created, for the most part, the quantum mechanical model. In 1926, he developed an equation that revised the Bohr model. -
Werner Heisenberg
In 1927, after studying quantum mechanics, Heisenberg published his Uncertainty Principle which stated that the position of particle or the momentum of the particle could be measured, but the more precisely one was measured, the more inaccurate the other measurement became. -
James Chadwick
In 1932, Chadwick conducted experiments that proved the existence of neutrons, which he imagined as a paired proton and electron. The discovery of neutrons accounted for the difference between an atomic mass and atomic number. -
Snow White
1937 – Snow White, Walt Disney’s first full-length animated film, is released. -
Karaoke
1971 – Karaoke machine invented. -
DNA fingerprints
1985 – DNA fingerprinting is used to assist police detective work. -
Julius Caesar- 100B.C.E.
100BC – Julius Caesar is born. -
Period: to
Atomic Theory Webquest Timeline
This website does not do B.C.E. Therefore, we put the B.C.E. in the description for the events that required this. Thank you for your understanding. Also, most of the years did not have specific dates, so ignore those. -
Jersey Shore!!
2009 – Jersey Shore premieres. -
Quantum Mechanical Model
The brain child of many scientists' idas and work, the quantum mechanical model is the most commanly accepted model as of today. It states that in the atom's shape, there is a 90% chance of finding an electron in the electron cloud around the nucleus.
