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Mar 14, 1000
Democritus
Democritus believed that all matter consisted of very small particles that coulld not be divided or seperated. He called the particles "atoms". He also believed that there were other atoms with different properties. -
Jun 18, 1000
Aristotle
Aristotle believed that there was not a limit to the number of times matter could be divided. To prove this, he used fire, air, water, and earth. Fire was a combination of hot and dry. Water was a combination of cold and wet. -
Antoine Lavoisier
Antoine Lavoisier was also called the "father of modern chemistry". He found oxygen and hydrogen, and also named them. He helped make the metric system, put together the list of elements, and helped reform chemical nomenclature. He also was the first to establish sulfur was an element. -
Joseph Louis Proust
Joseph Louis Proust believed that substances always combined in constant and definite proportions. Although a man named C.L. Berthollet did not believe this was true, Proust proved him wrong. -
John Dalton
John Dalton was interested in predicting weather. He studied the behavior of gases in the air. He did this by correctly concluding that a gas consists of individual particles. He gathered evidence of atoms by measuring the masses of elements that combine when compounds form. -
J.J. Thomson
Thomson discovered the electron that later lead to the "plum-pudding" model he invented. He pictured electrons in a sphere of positive electric charge. To prove this, Thomson used a sealed glass tube held with gas in the experiment. When he turned the current on, the disks became charged and a glowing beam appeared in the tube. Then, once he placed a charged plate on the outside of the tube, the beam bent toward it. -
Hantaro Nagaoka
Hantaro thought that an atom had a nucleus. He also found out that electrons move in orbit like rings around the planet Saturn. -
Ernest Rutherford
Ernest Rutherford discovered that uranium emits fast-moving particles that have a positive charge. He also named them "alpha particles". To prove this, he used a model to show that all of an atoms positive charge is concentrated on its nucleus. It also showed the path of a moving electron. -
Niels Bohr
Bohr had agreed with Rutherford's model that a nucleus is surrounded by a large volume of space. Bohr did the same thing except his focused on electrons. His model represents the planets moving around the sun. -
Erwin Schrödinger
Erwin Schrödinger developed mathematical equations that described the motion of electrons in atoms. His work lead to the electron cloud model. -
Ernest Marsden
Ernest Marsden was part of a famous experiment called the gold foil experiment. He worked on this with Ernest Rutherford. He later helped in World War I and studied radar research. -
James Chadwick
James Chadwick confirmed the existence of neutrons, which have no charge. He also said that atomic nuclei contain neutrons and positively charged protons. -
Louis de Broglie
Louis de Broglie showed that moving particles such as electrons have some properties of waves. A few years later his research or theory had evidence to support his idea.
