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460
Democritus
Democritus was born in 460 B.C. He believed atoms, or atomos, were particles that are not able to be divided. He thought there were different types of atoms with specific properties. Fo example, the atoms in liquids were smooth and the ones in solids were rough. His theory was made public in the 5th century B.C. -
470
Aristotle
Aristotle was born in 384 BC. He disagreed with Democritus. He thought there was an unlimited amount of times you could split an atom. His therory became public in 400 B.C. His model showed that all substances were made from only 4 elements- earth, air, fire, water. And had a combination of 4 qualities- hot, cold, dry. and wet. -
John Dalton
He thought everything was made up of tiny spherical matter, called atoms. He said they can not be divided, and has no internal structure. His contriubtion was made public in 1803. He made wooden spheres to represent the atoms of deifferent elements. -
Michael Faraday
He studied the affect of electricity on solutions.He came up with the term "Electrolysis" which means splitting molecules with electricity. -
JJ Thomson
JJ Thomson discovered the electron in 1897. He said "corpuscals" were the things atoms were made of. He used a sealed tube of gas in his experiments. When the current is turned on the disk was negatively charged and vice versa. Thomsons model has been called the "plum pudding model" after the dessert. -
Hantaro Nagaoka
Nagaoka was the first to defend the "Saturnian atomic model", which is that electrons orbit around an atom like the rings around Saturn. He announced this at Tokyo society for mathematics and physics in December 1903. -
Ernest Rutherford
In 1899 Rutherford discovered alpha particles. In 1909 Rutherfurd confronted one of his students, Marsden, to experiment and find out what happens to the alpha particles when they pass through a thin sheet of gold. The aplha particles which paths were deflected came close to another charged object. Rutherford had discovered tha nucleus. He thought all of an atoms postive charge was concentrated in its nucleus. -
Niels Bohr
Bohr agreed with Rutherfords model, a nucleus surrounded by a large volume of space. But he focused more on the electrons. In his model, the electrons moved in a fixed orbit around the nucleus. He made his model public in 1903. -
Erwin Schrodinger
Schrodinger took the ideas from de Broglie and other scientists and put them together in a single equation that is named after him, The Schrodinger Equation. This equation became public in 1926. This equation is still used today to understand atoms and molecules. His work lead to the electron cloud model. -
Ernest Marsden
In 1909 Ernest Marsden was instructed by Ernest Rutherford to see what happens to alpha particles when they pass through a thin sheet of gold. Because of the fact that they worked together, Mr. Rutherford and Marsden have the same model and theory. -
James Chadwick
James Chadwick confirmed the existence of neutrons, which does not have any electric charge. He learned that neutrons help stabilize the protons in an atom's nucleus. His discovery became public in 1932. -
Louis de Broglie
He proposed that, like light, electrons could act like both particles and waves. His theory was made public in 1924. De Broglie's hypothesis was proven correct when other scientists created experiments where electron beams could be bent. -
Dmitri Mendeleeff
He arranged elements into seven groups with similar properties. He found "the properties of the elements were periodic functions of their atomic weights". This is known as the Periodic Law.
