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300
Aristotle Bc
Aristotle did not believe in the atomic theory and he taught so otherwise. He thought that all materials on Earth were not made of atoms, but of the four elements, Earth, Fire, Water, and Air. He believed all substances were made of small amounts of these four elements of matter. Most people followed Aristotle’s idea, causing Democritus’ idea- which was that all substances on Earth were made of small particles called atoms- to be overlooked for about 2,000 years! -
400
Democritus (bc)
The theory of Democritus held that everything is composed of atoms, which are physically, but not geometrically, indivisible; that between atoms, there lies empty space; that atoms are indestructible; have always been, and always will be, in motion; that there are an infinite number of atoms, and kinds of atoms, which differ in shape, and size. Of the mass of atoms, Democritus said The more any indivisible exceeds, the heavier it is. But his exact position on weight of atoms is disputed. -
Antonie Lavosier
named the elements carbon, hydrogen and oxygen; discovered oxygen’s role in combustion and respiration; established that water is a compound of hydrogen and oxygen; discovered that sulfur is an element, and helped continue the transformation of chemistry from a qualitative science into a quantitative one -
Joseph Proust
developed the use of hydrogen sulfide as a reagent give results of his chemical analyses in terms of percentage weights -
Louisiana purchase
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John Dalton
Dalton being led by his search for an explanation of the law of multiple proportions to the idea that chemical combination consists in the interaction of atoms of definite and characteristic weight, the idea of atoms arose in his mind as a purely physical concept, forced upon him by study of the physical properties of the atmosphere and other gases. -
Amadeo Avagadro
gained recognition for his hypothesis, which was also known as ‘Avogadro’s Law’. He stated and published his theory in 1811. This law elucidates that at a fixed temperature and pressure, equal volumes of gases contain the same number of molecules regardless of their chemical nature and physical properties. -
Abe Lincoln
abe lincoln was assassinated -
William Crookes
Discovered cathode rays had the following properties: travel in straight lines from the cathode; cause glass to fluoresce; impart a negative charge to objects they strike; are deflected by electric fields and magnets to suggest a negative charge; cause pinwheels in their path to spin indicating they have mass. -
Madame Curie
conducting her own experiments on uranium rays. She discovered that the rays remained constant, no matter the condition or form of the uranium. The rays, she theorized, came from the element's atomic structure. This revolutionary idea created the field of atomic physics and Curie herself coined the word radioactivity to describe the phenomena. -
J.J. Thomson
Used a CRT to experimentally determine the charge to mass ratio (e/m) of an electron =1.759 x 10 8 coulombs/gram. -
Henri Becquerel
By accident, he discovered that the uranium salts spontaneously emitted a penetrating radiation that could be registered on a photographic plate. Further studies made it clear that this radiation was something new - not the same type as X-rays. He had discovered a new phenomenon - radioactivity. -
Max Planck
used the idea of quanta (discrete units of energy) to explain hot glowing matter. -
Robert Millikan
Oil drop experiment determined the charge (e=1.602 x 10 -19 coulomb) and the mass (m = 9.11 x 10 -28 gram) of an electron. -
Ernest Rutherford
Using alpha particles as atomic bullets, probed the atoms in a piece of thin (0.00006 cm) gold foil . He established that the nucleus was: very dense,very small and positively charged. He also assumed that the electrons were located outside the nucleus. -
Henry Ford
Henry ford starts production of the assmebly line -
Henry Moseley
Using x-ray tubes, determined the charges on the nuclei of most atoms. He wrote"The atomic number of an element is equal to the number of protons in the nucleus". This work was used to reorganize the periodic table based upon atomic number instead of atomic mass. -
Albert Einstein
best known for his work on relativity, and his simple but elegant equation E=MC2 , which expresses an equivalence between energy and matter. It is this equation that describes the possibility of the transformation of mass into energy, and the phenomenon that is operational in a nuclear power plant or nuclear bomb. Very little matter can become an inordinate amount of energy, as the speed of light is a constant having an inordinately large value. -
Niels Bohr
Developed an explanation of atomic structure that underlies regularities of the periodic table of elements. His atomic model had atoms built up of sucessive orbital shells of electrons. -
Louis deBroglie
Discovered that electrons had a dual nature-similar to both particles and waves. Particle/wave duality. Supported Einstein. -
Werner Heisenberg
Described atoms by means of formula connected to the frequencies of spectral lines. Proposed Principle of Indeterminancy - you can not know both the position and velocity of a particle. -
Erwin Schrodinger
Viewed electrons as continuous clouds and introduced "wave mechanics" as a mathematical model of the atom. -
James Chadwick
Using alpha particles discovered a neutral atomic particle with a mass close to a proton. Thus was discovered the neutron. -
Pearl Harbor
Pearl Harbor was attacked by the Japanese -
Barack Obama
Born this date -
Apple
Apple was launched