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350 BCE
Democritus vs. Aristotle
Democritus argued that everything can be imagined to be made up of tiny pieces of pure substances. He called the tiny pieces atomos.
Aristotle argued that everything was instead made up of the four elements: Air, Earth, Fire, Water. These things are in balance. -
Period: 350 BCE to
Alchemists
During this time, alchemists attempted to turn one substance into another, and hid their experiments from one another. -
Francis Bacon and Robert Boyle
Sir Francis Bacon and Robert Boyle were both skeptics of the way alchemists were doing their work. Francis Bacon proposed inductive logic instead of deductive, so that they could use incomplete evidence, but still come to anstrong conclusion. Robert Boyle wrote a work called "The Skeptical Chymist", in which he proposed there were more than 4 elements. -
Antoine Lavoisier: the Father of Modern Chemistry
Lavoisier was a very dilligent chemist. He was the first to compile the works and experiments of many chemists into the first textbook. He did this so that future chemists could use it as a reference when they were doing their own experiments. -
Discovery of Oxygen
In one of Lavoisier's experiments, he used mercury in a swan neck flask and a sealed chamber to isolate one element from the air trapped instide. He called this element Oxygen, and found that it makes up about 1/5 th of the atmosphere. -
Period: to
Chemists: Lavoisier, Liebig and others
These chemists work together to try to find proportions of elements in organic substances. They used a series of combustion reactions to determine the ratios of elements. -
John Dalton's Atomic Theory
Dalton’s Atomic Theory:
All matter is made of extremely small atoms, which cannot be subdivided, created or destroyed.
Atoms of a given element are identical in their physical and chemical properties.
Atoms of different elements differ in their physical and chemical properties.
Atoms of different elements combine in simple, whole-number ratios to form compounds.
In chemical reactions, atoms are combined, separated, or rearranged but never created destroyed, or changed. -
Mendeleev's Table
Dimitri Mendeleev was one of the first to try and organize the known elements. He considered all the information on elements that had been discovered and found trends when he arranged them by relative mass. The trends that he used as a secondary sort were affinity, reactivity, and physical properties. -
Goldstein's Crook's Tube
A chemist names Eugene Goldstein used a crook's tube in his experiment. He discovered that atoms have some sort of electrical charge. -
J.J. Thomson's Cathode Ray.
Thomson worked with a cathode ray tube to study the electrical charge of atoms. He found subatomic paricles (that were named electrons), which meant that Dalton's theory was faulty. He proposed a different model of an atom: the plum pudding model, -
Milikan's Oil Drop
Millikan devised a special apparatus to suspend small oil drops between two electrical metal plates. He did this to determine the electrical charge of an electron. He found the charge of one electron to be 1.5924(17)x10-19 Coulombs -
Period: to
Atoms
Ernest Rutherford conducted the gold foil experiment to find what atoms looked like. He shot alpha particles at a piece of gold foil to see what pattern they went through in. Based on the results, he determined that Thomson's model was wrong. He redesigned the model into a nuclear model. -
Period: to
James Chadwick
After repeated experiments bombarding Beryllium atoms with alpha radiation, Chadwick had evidence of a new kind of radiation, the neutron. It had the same mass as a proton, but was neutrally charged. He was awarded the Nobel Prize in Physics for his discovery in 1935. -
Sources
- Mrs. Seganish's Units 1 and 2 slides