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Democritus
Living from about 460-370BCE, Democritus was the philosopher who first proposed the idea of an atom. Democritus lived in Abdera, Thrace and Miletus in Greece, and it was here where he came up with the idea that there were minisucle particles that existed in a void. He named these after the greek word atomus which means "Indivisible". He proposed that they cannot be broken down, destroyed, and are invisible. Democritus did no studies or experiments because he was a philosopher. -
Antoine Lavoisier
Antoine Lavoisier was born into a rich family on August 26, 1743 and grew up practicing law to follow his fathers footsteps. Lavoisier studied science in his spare time and eventually turned away from law and made great scientific discoveries. He created the Law of Conservation of Matter which says that matter cannot be created or destroyed; only changed. He found this by burning matter in sealed jars and discovering that the contents still weighed the same. -
John Dalton
John Dalton, also known as "The Father of the Modern Atomic Theory", was born on September 6, 1766 and died on July 27, 1844. He lived in England, where he proposed that matter was made of tiny atoms, and all of the atoms of an element are identical. He discovered this by experimenting with gasses, and found that water absorbs some gasses better than others. -
J.J. Thomson
J.J. Thomson was born on December 18, 1856 and died on August 30, 1940, but before he died he made the discoverey of the negativly charged electron. He was experimenting with a cathode ray and found that some particles in the atom were attracted to a postitive charge, and concluded that there must be a negativly charged particle. He also made the "plum pudding" model of the atom, which said that the atom was a positivly charged sphere with negativly charged electrons embedded in it. -
Marie Curie
Marie Curie was a female scientist who lived in france where she made several discoveries. Curie discovered that radioactivity does not come from the way atoms are arranged, but they exist in the atoms already. She experimented with many atoms to find radioactivity in them and even discovered two elements called Radium and Polonium -
Robert Millikan
Robert Millikan was born on March 22, 1868 and spent most of his life studying and experimenting in the United States. He used the Oil Drop experiment to find the charge of the electron by observing the charge of oil drops sprayed between two metal plates.. Millikan discovered that the charge of and electron was 1.6x×10−19 coulombs. Millikan recieved the Nobel Prize in 1923 for his contributions to physics -
Ernest Rutherford
Ernest Rutherford was a scientist who lived in New Zealand and died on October 19,1937. Rutherford was also titled First Baron of Nelson, New Sealand. He made the important discovery of the positivly charged nucleus of an atom while doing the gold foil expermient. He also found that the nucleus was densly packed into a small sphere at the center of the mostly empty atom. -
Niels Bohr
The Danish scientist, Niels Bohr, lived from 1885 to 1962 and completed many studies on Atomic Structure in England. One of his most important discoveries was of the Atom's energy levels for electrons. Bohr used the hydrogen emission spectrum to add energy to a hydrogen atom, and when energy was added electrons moved. This discovery led him to propose his model of the atom, which had electrons travelling around the nucleus in fixed orbits. -
James Chadwick
James Chadwick was a scientist who lived during the 1800's and 1900's and studied atomic structure. He is responsible for the discovery of the neutral atomic particle known as the neutron. He discovered this particle by launching high speed positive alpha particles at Beryllium. James Chadwick also made huge contributions to the creation of the atomic bomb in World War II. -
Werner Heisenburg
Werner Heisenburg was a German scientist who lived during the 1900's. Before he died in 1976, Heisenburg made many contributions to the study of quantum mechanics. He contributed to the development of the atomic theory by creating the uncertainty priciple. This stated that electrons dont travel in neat orbits. Even when he was captured by american troops and sent to England in WWII he still kept on working.
