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431 BCE
Peloponessian War
The Peloponnesian war was a war between the Greek city-states of Athens and Sparta, and each of their respective allies. -
Period: 431 BCE to
History of an Atom- Penny Fillion
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Period: 431 BCE to
History of an Atom
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430 BCE
Democritus discovery
Democritus (460-370 BCE) discovered that everything is made of atoms, or as he called them atomos. This changed how people viewed the world around them. He believed they were uniform, small, and indestructible. -
Jefferson's presidency
Thomas Jefferson’s first presidency began in 1800. -
John Dalton's discovery
Dalton (1776-1844) atomic theory suggested that all matter was composed of indivisible and indestructible atoms with distinct masses and properties, the combination of which determined the physical nature of their constituent elements. -
Michael Faraday's discovery
Michael Faraday (1791-1867) discovered electromagnetic induction, in which a current would run through water, separating the molecules of the substance into their pure atoms. He was the first to discover that atoms have an electrical component, which would later be known as the electron. -
Cholera outbreak
In 1832, a cholera outbreak closely linked with unclean drinking water ravaged New York City. -
Eugen Goldstein
Eugen Goldstein (1850-1930) discovered positive rays, or Canal rays. These are positive ions that accelerate through an evacuated tube. His discoveries on the cathode ray would later develop to the discovery of the electron. -
JJ Thompson
JJ Thompson (1856-1940) created a model of the atom that was the first model to include an internal structure, after Thompson previously discovered the electron in 1897. His model proposed negatively charged electrons within a positively charged “soup”. This model failed to explain many phenomena, which is why it is now obsolete. -
Robert Millikan
Robert Millikan (1868-1953) oil drop experiment proved that there was an electron, and accurately predicted its charge. He also discovered that all electrons carry the same amount of negative charge. His experiment was the first to predict the charge held by one electron. -
Ernest Rutherford
Rutherford (1871-1937) discovered that an atom is nearly all empty space, with nearly all of its mass concentrated in the nucleus center. He found that the nucleus is positive, and is surrounded by positive and negatively charged electrons. Rutherford was the first to theorize that the nucleus was surrounded by electrons in orbit. -
Niels Bohr
Niels Bohr (1885-1962) proposed the theory of a hydrogen atom, that electrons move around in a pre-destined way, and if the electron moves to a lower orbit the difference is sent out in radiation. His model stated that electrons only have specific energy levels available. His model was groundbreaking because it was the first to show electrons orbiting in specific ways around the nucleus, containing protons. -
World War I
In 1914, Austria-Hungary declared war on Serbia. This first declaration, with many following soon after, officially began the global conflict now known as World War I. -
End of World War I
In 1918, World War I came to an end. -
Edwin Schrodinger
Edwin Schroedinger (1887-1961) was an Austrian theoretical physicist known for his thought experiment “Schrodinger's cat.” His model, unlike Bohr’s model, did not have the electrons following specific orbits, and instead had the electrons moving quickly and forming a cloud around the nucleus of the atom. He also formulated a wave equation that calculated the energy level of electrons. -
Werner Heisenberg
Werner Heisenberg (1901-1976) discovered the Uncertainty Principle. This principle stated that it can never exactly be known both a particle’s momentum and location. This means that the more precise the location, the more uncertain the momentum. This is important because it helps physicists understand things at the atomic level. -
Stock Market Crash
“Black Friday”, or the stock market crash, happened in 1929 in America. This event started the Great Depression, which lasted 10 years. -
James Chadwick
James Chadwick (1891-1974) made a revolutionary discovery about the atom, that there were neutral molecules called neutrons that have no charge. These neutrons are with the protons in the center of the atom, and provide no change but create isotopes and change the atomic weight if there are more or less. This was very important for nuclear physics, as it meant that the neutrons would not be repelled by the positive protons as it entered the nucleus, making it ideal to probe the nucleus with. -
World War II
Adolf Hitler's invasion of Poland started the second large-scale global conflict now known as World War II in September of 1939.