Chemical 2nd year

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Chemistry is a branch of science that has been around for a long time. In fact, chemistry is known to date back to as far as the prehistoric times. Due to the amount of time chemistry takes up on the timeline, the science is split into four general chronological categories. The four categories are: prehistoric times - beginning of the Christian era (black magic), beginning of the Christian era - end of 17th century (alchemy), end of 17th century - mid 19th century (traditional chemistry) and mid 19th century - present (modern chemistry).


Time Intervals
Specific Times
Events
Description


Prehistoric Times -
Beginning of the Christian Era

(Black Magic)

http://tqd.advanced.org/2690/hist/black.html

1700 BC
King Hammurabi's reign over Babylon
Known metals were recorded and listed in conjunction with heavenly bodies.

430 BC
Democritus of ancient Greece
Democritus proclaims the atom to be the simplest unit of matter. All matter was composed of atoms.

300 BC
Aristotle of ancient Greece
Aristotle declares the existence of only four elements: fire, air, water and earth. All matter is made up of these four elements and matter had four properties: hot, cold, dry and wet.

Beginning of the Christian Era -
End of 17th Century

(Alchemy)

http://tqd.advanced.org/2690/hist/alchemy.html



300 BC -
300 AD
The Advent of the Alchemists
Influenced greatly by Aristotle's ideas, alchemists attempted to transmute cheap metals to gold. The substance used for this conversion was called the Philosopher's Stone.

13th Century (1200's) - 15th Century (1400's)
Failure of the Gold Business
Although Pope John XXII issued an edict against gold-making, the gold business continued. Despite the alchemists' efforts, transmutation of cheap metals to gold never happened within this time period.

1520
Elixir of Life
Alchemists not only wanted to convert metals to gold, but they also wanted to find a chemical concoction that would enable people to live longer and cure all ailments. This elixir of life never happened either.

End of 17th Century
Death of Alchemy
The disproving of Aristotle's four-elements theory and the publishing of the book, The Skeptical Chemist (by Robert Boyle), combined to destroy this early form of chemistry.




End of 17th Century -

Mid 19th Century

(Traditional Chemistry)



http://tqd.advanced.org/2690/hist/traditional.html






1700's


Phlogiston Theory
Coulomb's Law

Johann J. Beecher believed in a substance called phlogiston. When a substance is burned, phlogiston was supposedly added from the air to the flame of the burning object. In some substances, a product is produced. For example, calx of mercury plus phlogiston gives the product of mercury.

Charles Coulomb discovered that given two particles separated by a certain distance, the force of attraction or repulsion is directly proportional to the product of the two charges and is inversely proportional to the distance between the two charges.

1774-1794
Disproving of the Phlogiston Theory
Joseph Priestley heated calx of mercury, collected the colorless gas and burned different substances in this colorless gas. Priestley called the gas "dephlogisticated air", but it was actually oxygen. It was Antoine Lavoisier who disproved the Phlogiston Theory. He renamed the "dephlogisticated air" oxygen when he realized that the oxygen was the part of air that combines with substances as they burn. Because of Lavoisier's work, Lavoisier is now called the "Father of Modern Chemistry".

1803
Dalton's Atomic Theory
John Dalton publishes his Atomic Theory which states that all matter is composed of atoms, which are small and indivisible.



Mid 19th Century -

Present

(Modern Chemistry or

20th Century Chemistry)



http://tqd.advanced.org/2690/hist/modern.html






1854
Vacuum Tube
Heinrich Geissler creates the first vacuum tube.

1879
Cathode Rays
William Crookes made headway in modern atomic theory when he used the vacuum tube made by Heinrich Geissler to discover cathode rays. Crookes created a glass vacuum tube which had a zinc sulfide coating on the inside of one end, a metal cathode imbedded in the other end and a metal anode in the shape of a cross in the middle of the tube. When electricity was run through the apparatus, an image of the cross appeared and the zinc sulfide glowed. Crookes hypothesized that there must have been rays coming from the cathode which caused the zinc sulfide to fluoresce and the cross to create a shadow and these rays were called cathode rays.

1885
The Proton
Eugene Goldstein discovered positive particles by using a tube filled with hydrogen gas (this tube was similar to Thomson's tube...see 1897). The positive particle had a charge equal and opposite to the electron. It also had a mass of 1.66E-24 grams or one atomic mass unit. The positive particle was named the proton.

1895
X-rays
Wilhelm Roentgen accidentally discovered x-rays while researching the glow produced by cathode rays. Roentgen performed his research on cathode rays within a dark room and during his research, he noticed that a bottle of barium platinocyanide was glowing on a shelf. He discovered that the rays that were causing the fluorescence could also pass through glass, cardboard and walls. The rays were called x-rays.

1896
Pitchblend
Henri Becquerel was studying the fluorescence of pitchblend when he discovered a property of the pitchblend compound. Pitchblend gave a fluorescent light with or without the aid of sunlight.

1897


The Electron and Its Properties
Radioactive Elements

J.J. Thomson placed the Crookes' tube within a magnetic field. He found that the cathode rays were negatively charged and that each charge had a mass ratio of 1.759E8 coulombs per gram. He concluded that all atoms have this negative charge (through more experiments) and he renamed the cathode rays electrons. His model of the atom showed a sphere of positively charged material with negative electrons stuck in it. Thomson received the 1906 Nobel Prize in physics.

Marie Curie discovered uranium and thorium within pitchblend. She then continued to discover two previously unknown elements: radium and polonium. These two new elements were also found in pitchblend. She received two nobel prizes for her discovery; one was in chemistry while the other was in physics.

1909
Mass of the Electron
Robert Millikan discovered the mass of an electron by introducing charged oil droplets into an electrically charged field. The charge of the electron was found to be 1.602E-19 coulombs. Using Thomson's mass ration, Millikan found the mass of one electron to be 9.11E-28 grams. Millikan received the 1932 Nobel Prize in Physics for this discovery.

1911
Three Types of Radioactivity
Ernest Rutherford sent a radioactive source through a magnetic field. Some of the radioactivity was deflected to the positive plate; some of it was deflected to the negative plate; and the rest went through the magnetic field without deflection. Thus, there were three types of radioactivity: alpha particles (+), beta particles (-) and gamma rays (neutral). By performing other experiments and using this information, Rutherford created an atomic model different from Thomson's. Rutherford believed that the atom was mostly empty space. It contains an extremely tiny, dense positively charged nucleus (full of protons) and the nucleus is surrounded by electrons traveling at extremely high speeds. The Thomson model was thrown out after the introduction of the Rutherford model.

1914
Protons within a Nucleus
Henry Moseley attempts to use x-rays to determine the number of protons in the nucleus of each atom. He was unsuccessful because the neutron had not been discovered yet.

1932


The Neutron
Neutron Bombardment and Nuclear Fission

James Chadwick discovers the neutron.

Enrico Fermi bombards elements with neutrons and produces elements of the next highest atomic number. Nuclear fission occurred when Fermi bombarded uranium with neutrons. He received the 1938 Nobel Prize in physics.

1934
Artificial Radioactive Elements
Irene Curie and Frederic Joliot-Curie discovered that radioactive elements could be created artificially in the lab with the bombardment of alpha particles on certain elements. They were given the 1935 Nobel Prize.

1940's
Manhattan Project
Albert Einstein and Enrico Fermi both warned the United States about Germany's extensive research on atomic fission reaction. Below the football field at the University of Chicago, the United States developed the very first working nuclear fission reactor. The Manhattan Project was in process.