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100
Democritus
460-370 B.C.
Proposed the concept of the atom
-Matter is composed of empty space through which atoms move.
-Atoms are solid, homogeneous, indestructible, and indiviseble.
-Different kinds of atoms have different sizes and shapes.
-The differing properties of matter are due to the size, shape, and movement of atoms.
-Apparent changes in matter result form changes in the groupings of atoms and not from changes in the atoms themselves. -
110
Aristotle
384-322 B.C.
Rejected the concept of the atom
-One of the most influential philosophers.
-Wrote extensively on may subjects, including politics, ethics, nature, physics, and astronomy.
-Most of his writings have been lost through the ages. -
Sep 24, 1492
Christopher Columbus
VideoIn this year Columbus sailed the oceans and found the Americas -
John Dalton
1766-1844
Breakthough in our understanding of matter because of atomic theory.
-All matter is composed of extremely small particles called atoms.
-All atoms of a given elemtent are identical, having the same size, mass, and chemical properties. Atoms of a specific element are different from those of any other element.
-Atoms cannot be created, divided into smaller particles, or destroyed. -
John Dalton Continued
-Different atoms combine in simple wholenumber ratios to form compounds.
-In a chemical reaction, atoms are separated, combined, or rearranged. -
The American Revolution
1775-1781 the Americans fought against their mother country of Great Britian and won after a long bloody war. -
Joseph Proust
1754-1826
Proved the idea that every pure chemical compound consists of elements in a definite proportion. Developed the use of hydrogen sulfide as a reagent. Gave results of his chemical analyses in terms of percentage weights. -
Antoine Lavoisier
1743-1794
Compiled a list of the 23 elements known at the time. -
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Amedio Avogadro
1776-1856
Determined the volume of one mole of a gass. 6.02 X 10^23 -
William Crookes
1832-1919
Noticed a flash of light within one of the tubes in his darkened laboratory
-flash was a produced because radiation was striking a light-producing coationg that had been applied to the end of the tube.
-Figured out these flashes where rays traveling from the cathode to the anode within the tube.
-Called a cathode ray
-this discovery lead to the television and computer monitor -
The Civil War
The war between the north and the south over slavery lasted from 1861 to 1865. In the end the north won and slavery was abolished. -
Abraham Lincoln
Lincoln was assassinated in this year by John Wilkes Booth at Ford's Theatre in Washington D.C. -
J.J. Thomson
1856-1940
Experiments with cathode ray tube to determine the ratio of its charge to its mass
-Plum pudding atomic model proposed that negatively charged electrons were distributed throughout a uniform positve charge -
Henri Becquerel
1852-1908
Studied minerals that emit light after being exposed to sunlight. Discovered that phosphorescent uranium salts produce spontaneous emissions that darken photographic plates even when not exposed to light. -
Max Planck
1858-1947
Studied the light emitted from heated objects.
Matter can gain or losse energy only in small, specific amounts called quanta. Quantum is the minimum amount of energy that can be gained or lost by an atom. -
Marie Curie
1867-1934
Isolated the components emitting the rays in Becquerel's mineral sample. Darkening of plates was because of uranium atoms persent in the mineral sample when rays where emitted. Named the process by which materials give off such rays as radioactivity. Identified the two new elements polonium and radium because of radioactivity. -
Albert Einstein
1879-1955
Electromagnetic radiation has both wavelike and particlelike natures. as beam of light has many wavelike charateristics, it also can be thought of as a stream of tiny particles, or bundles of energy, called photons, photons are particles of electromagnetic radiation with no mass that carries a quantum of energy -
Robert Millikan
1868-1953
Determined the charge of an electron -
Ernest Rutherford
1871-1937
His experimenting proved Thomson's plum pudding model wrong.
-most of an atom consists of electrons moving rapidly through empty space. The electrons move through the available space surrounding the nucleus and are held within the atom by their attraction to the positively charged nucleus. Very small and dense nucleus.
-The nucleus contains positively charged particles called protons -
Henry Moseley
1887-1915
Discoved that atoms of each element contain a unique positive charge in their nuclei. The number of protons in an atom identifies it as an atom of a particular element. The number of protons in an atom is referred to as the element's atomic number. -
Niels Bohr
1885-1962
Proposed a quantum model for the hydrogen atom that seemed to answer this question. Model also correctly predicted the frequencies of the lines in hydrogen's atomic emission spectrum. Related the hydrogen atom's energy states to the motion of the electron within the atom -
Louis de Broglie
1892-1987
Thought that Bohr's quantized electron orbits had characteristics similar to those of waves. The de Broglie equation predicts that all moving particles have wave characteristics. -
Werner Heisenberg
1901-1976
It is impossible to make any measurement on an object without disturbing the object. The Heisenberg uncertainty priciple is that it is fundamentally impossible to know percisely boht the velocity and position of a particle at the same time. -
Erwin Schrodinger
1887-1961
Treated the hydrogen atom's electron as a wave. The quantum mechanical model of the atom is an atomic model in which electrons are treated as waves, also called the wave mechanical model of the atom. Model attempts to describe the electron's path around the nucleus. -
James Chadwick
1891-1974
Nucleus also contains another subatomic particle, called a neutron that whas a neutral particle -
Adolf Hitler
Committed suicide after it became evident that he would not take over the world after causing WWII. -
Assassination of John F. Kennedy
In this year JFK was assassinated by Lee Harvey Oswald -
Apollo 11
VideoApollo 11 was the first moon landing ever made and this was done by the United States of America. -
September 11, 2001
Video4 american planes where taken controll of by terrorists. This started the war against terror. -
Death of Osama bin Laden
VideoDied when American soildiers found where he was hiding and shot him while they searched the house.
