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460 BCE
Democritus
(460-370 B.C.E)
Abdera, Thrace
He was the first to think that everything was made of particles, started atom theory. He did so by thinking that everything had to be made up of tiny particles and that it differed between objects. -
Antoine Lavoisier
(1743-1794)
France
He created the law of Conservation of Energy, which is, energy cannot be created or destroyed. He found it by conducting an experiment that involved heating mercury oxide. Its weight would decrease and the oxygen that was released was equal to the amount the mercury oxide decreased. -
John Dalton
(1766-1844)
England
He published a book with something that is now called Dalton’s Law (contains 6 of his laws). Created a diagram to show how atoms might combine to create a molecule. Also created a diagram on how a water molecule might look. Thought of these by comparing the masses of two elements and then simplifying them. -
J.J. Thomson
(1856-1940)
England
He discovered the electron by using a cathode ray tube. He observed how far the rays would travel before they stopped. The Plum Pudding Model was also one of his creation, which was later proved wrong. Also discovered that there are stable elements through isotopes. This was found because his research student used a mass spectrometer, which showed that an element can exist in more than one form. -
Max Planck
(1858-1947)
Germany
Max Planck mainly studied thermodynamics throughout his life, and it's thermodynamics that made him so famous. He was very interested in radiation deriving from hot materials. He came up with a radical theory which stated that energy did not flow steadily, but rather came in small packets called quanta. He thought this explained why a hot iron poker glowed red and white. This idea revolutionized physics. -
Marie Curie
(1867-1934)
Poland and Paris
She and her husband discovered Polonium and Radium, finding that they were far more radioactive than Uranium. Also came up with the term radioactivity. She thought of this after studying so many elements sharing radioactivity. -
Robert Millikan
(1868-1953)
Illinois and California
Found the charge of a single electron. His first try of proving it was measuring a water droplets, but wasn’t very accurate. More precise results came from his oil drop experiment. -
Ernest Rutherford
(1871-1937)
New Zealand and England
He two different types of radiation that he named alpha and beta. He did so by allowing radiation from uranium to go through increasing numbers of foil. Discovered the nucleus by performing an experiment with gold foil. This was done by seeing how many alpha and beta particles passed through. -
Albert Einstein
(1879-1955)
Germany and others
Brownian motion has to do with the constant, random fluctuations in small particles. Brownian motion was proved to be higher at higher temperatures due to a higher kinetic energy which cause atoms to move more rapidly. Einstein believed that these movements could be passed on to larger particles. So the higher the temperature of something the more larger particles would be affected, possibly up to the point that it could be observed through a microscope. -
Niels Bohr
(1885-1962)
Denmark
Niels Bohr made a revolutionary model of the atom which shows the positively charged nucleus in the middle surrounded by negatively charged electrons. It was much like our solar system, except electromagnetic force held it all together instead of gravity. It was thought that the electrons followed certain orbits at certain distances from the nucleus, if an electron moved closer to the nucleus it emitted a photon. This became his basis for quantum theory. -
Erwin Schrodinger
(1887-1961)
Austria
Schrodinger came up with the electron cloud model. Until he said differently, the Bohr model was the most widely accepted model. It showed electrons on a fixed orbit around the nucleus. He believed this wasn't true though. He believed that they didn't follow set paths, but instead had a general area in which they could be found. He came up with an equation which showed the probability that electrons would be in certain places at certain times. -
James Chadwick
(1891-1974)
Europe
The belief during chadwicks time was that there were only protons and electrons and the electrons were both inside and outside of the nucleus. Chadwick however, did not believe this. He believed that there were particles with no charge in the nucleus. He found them by using polonium and bombarding wax with these particles. The protons reacted as if they'd been hit with an electrically neutral particle with a similar mass, he’d discovered the neutron. -
Louise De Broglie
(1892-1987)
France
Louise de Broglie was one of the first scientists to theorize about the wave nature of matter. Albert Einstein came up with the idea that light acted as both a particle and a wave. It could be affected by gravity like a particle but moved like a wave, Broglie theorized that this was true for all matter. -
Werner Heisenberg
(1901-1976)
Germany
Heisenberg created a new theory based on what can be observed, like the radiation emitted from an atom. He believed that you couldn't put electrons in a specific place in time. In fact, he believed you couldn't even follow an electron's orbit. Because of this belief he said that Bohr's model can't be true. He said that set values such as position and velocity could not be used, he said that we should use abstract mathematical structures called “matrices”.
