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400 BCE
Current Events in 400 BCE
The Egyptians successfully revolt against Persian rule. The Carthaginians occupy Malta. After Cyrus has been killed, his Greek mercenaries make their way back to Greece, where Sparta is so impressed with their feats in and march through Persia that they declare war on the Persians. -
400 BCE
Democritus Atom Model (460-370 BCE)
Democritus changed the model of the atom by making it look uniform, solid, hard, incompressible, and indestructible. -
Period: 400 BCE to
The Atomic Models Throughout History
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Current Event Around 1803
Thomas Jefferson was elected President of the United States by the House of Representatives, following a tie in the Electoral College. -
John Dalton Atomic Model (1766-1844)
The model was changed to have mass units and more than 1 ball. -
Michael Faraday Atomic Model (1791-1867)
Michael Faraday discovered that atoms had an electricity to them. Demonstrating that a changing magnetic field induces an electric current in a nearby circuit showed that mechanical energy can be converted to electric energy. -
Eugene Goldstein Atomic Model (1850-1930)
Eugen discovered evidence of a positively charged particle, which would later be called the Proton. -
JJ Thomson Atomic Model (1856-1940)
He discovered that all atoms contain tiny negatively charged subatomic particles or electrons. -
World Event within 10 years of Thomson’s discovery
Albert Enisteins theory of relativity: he same laws of physics hold true in all inertial reference frames and that the speed of light is the same for all observers, even those moving with respect to one another. -
Ernest Rutherford Atomic Model (1871-1937)
In the nuclear atom, the protons and neutrons, which comprise nearly all of the mass of the atom, are located in the nucleus at the center of the atom. -
Neils Bohr Atomic Model (1885-1962)
In the Bohr Model the neutrons and protons (symbolized by red and blue balls in the adjacent image) occupy a dense central region called the nucleus, and the electrons orbit the nucleus much like planets orbiting the Sun. -
Robert Millikan Atomic Model (1868-1953)
Millikan's work demonstrated that electrons did have a discrete, quantifiable charge. Thomson had also already calculated the charge-to-mass ratio of an electron, so once Millikan was able to measure the elementary charge, the mass of an electron could also be calculated. -
World Event within 10 year's of Bohr's discovery
The Treaty of Versailles subjected Germany to strict punitive measures. The Treaty required the new German Government to surrender approximately 10 percent of its prewar territory in Europe and all of its overseas possessions. -
Erwin Schroedinger Atomic Model (1887-1961)
The electron cloud model was developed in 1926 by Erwin Schrödinger and Werner Heisenberg. The model is a way to help visualize the most probable position of electrons in an atom. The electron cloud model is currently the accepted model of an atom. -
Werner Heisenberg Atomic Model (1901-1976)
Heisenberg objected to the current model because he claimed that since one couldn’t actually observe the orbit of electrons around a nucleus, such orbits couldn’t really be said to exist. One could only observe the spectrum of light emitted or absorbed by atoms. Starting in 1925, Heisenberg set to work trying to come up with a quantum mechanics that relied only on properties that could, at least in theory, be observed. -
World Event within 10 years of Schroedinger’s discovery
The "Great Depression " was a severe, world -wide economic disintegration symbolized in the United States by the stock market crash on "Black Thursday", October 24, 1929 . The causes of the Great Depression were many and varied, but the impact was visible across the country. By the time that FDR was inaugurated president on March 4, 1933, the banking system had collapsed, nearly 25% of the labor force was unemployed, and prices and productivity had fallen to 1/3 of their 1929 levels. -
James Chadwick Atomic Model (1891-1974)
The atomic model after Chadwick's discovery consisted of what can be seen below; positively charged protons and neutral neutrons bound together as the atom's nucleus, with negatively charged electrons occupying energy levels surrounding the nucleus. -
World Event within 10 years of Chadwick’s discovery
Adolf Hitler's invasion of Poland in September 1939 drove Great Britain and France to declare war on Germany, marking the beginning of World War II. Over the next six years, the conflict took more lives and destroyed more land and property around the globe than any previous war.