-
465 BCE
Democritus hypothesized that atoms cannot be destroyed, differ in size, shape and temperature, are always moving, and are invisible.
-
460 BCE
Democritus Birth
-
442 BCE
First Atomic Model
Democritus made the first atomic model -
370 BCE
Democritus Death
-
Antoine Lavosier's Birth
He was recognized one of the most important chemical elements, oxygen.
He stated that during the process of combustion, not only is a substantial quantity of air used, but there is also a visible gain in the mass of the substance. -
John Dalton's Birth
September 6, 1766, Eaglesfield, Cumbria, United Kingdom -
The effects of combustion of phosphorus
It was in 1772 that Lavoisier found out the effects of combustion of phosphorus. He realized that the process required a lot of air and the consequence was a gain in mass. -
Antoine Lavosier's Death
-
The Theory of Atomism
The theory of atomism, proposed by Dalton in the early 19th century and derived from meteorological studies, is the foundation for our modern concept of the atom. -
The Theory of Atomism (Pt.2)
Elements are made of extremely small particles called atoms.
Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties.Atoms cannot be subdivided, created, or destroyed. Atoms of different elements combine in simple whole-number ratios to form chemical compounds. In chemical reactions, atoms are combined, separated, or rearranged. -
The Law of Multiple Proportions
Dalton developed the law of multiple proportions by studying and expanding upon the works of Antoine Lavoisier and Joseph Proust. -
John Dalton's Announcement of His Atomic Theory
John Dalton gave this Society the first announcement of his famous atomic theory -
Dalton and New System of Chemical Philosophy
Dalton consolidated his theories of Atomic weight in his New System of Chemical Philosophy (1808–1827). -
John Dalton's Death
July 27, 1844, Manchester, United Kingdom -
JJ Thomson's Birth
December 18, 1856, Cheetham Hill, Manchester, United Kingdom -
Max Planck's Birth
April 23, 1858, Kiel, Germany -
Robert Millikan's Birth
March 22, 1868, Morrison, Illinois, United States -
Ernest Rutherford's Birth
August 30, 1871, Brightwater, New Zealand -
Albert Einstein's Birth
March 14, 1879, Ulm, Germany -
Niels Bohr's Birth
October 7, 1885, Copenhagen, Denmark -
James Chadwick's Birth
October 20, 1891, Bollington, United Kingdom -
Louis de Broglie's Birth
August 15, 1892, Dieppe, France -
J. J. Thomson discovered the electron
J. J. Thomson discovered the electron in 1897 -
Max Planck suggests radiation is quantisized
-
Werner Heisenberg's Birth
December 5, 1901, Würzburg, Germany -
Period: to
Werner Heisenberg's Life
-
The Thomson Model
Thomson's plum pudding model of the atom in 1904 before the discovery of the atomic nucleus in order to include the electron in the atomic model. In Thomson's model, the atom is composed of electrons surrounded by a soup of positive charge to balance the electrons' negative charges, like negatively charged "plums" surrounded by positively charged "pudding". -
Cornerstone of Quantum Theory
Einstein published
a highly controversial proposal
concerning the nature of light, a
proposal that later formed a
cornerstone of quantum theory -
Einstein and The Validity of The Laws of Therodynamics
He published an analysis that pointed the way towards a crucial test of the reality of atoms, and of the validity of the laws of thermodynamics. -
The Size of Atoms and Molecules
Einstein devised a mathematical method of calculating
the size of atoms and molecules in early 1905 -
Einstein Published 1st Paper on Light
A paper on the particulate nature of light, in which he explained the “photoelectric effect” and certain other experimental results by proposing that light interacts with matter as discrete “packets” or quanta of energy, rather than as a wave. -
Einstein Published 2nd Paper
A paper explaining Brownian motion (the seemingly random movement of particles suspended in a fluid) as direct evidence of molecular action, thus supporting the atomic theory (that all matter is made up of tiny atoms and molecules). -
Einstein Published 3rd Paper
a paper, which has become known as the Special Theory of Relativity, on the electrodynamics of moving bodies, which showed that the speed of light is independent of the observer's state of motion, and introduced the idea that the space-time frame of a moving body could slow down and contract in the direction of motion relative to the frame of the observer. -
Einsten Published 4th Paper
A paper on mass-energy equivalence, in which he deduced the famous equation E = mc2 from his special relativity equations, suggesting that tiny amounts of mass could be converted into huge amounts of energy (which presaged the later development of nuclear power). -
Thomson Model: False!
The 1904 Thomson model was proved false by Hans Geiger's and Ernest Marsden's 1909 gold foil experiment. -
Robert A. Millikan's Earliest Sucess
His earliest major success was the accurate determination of the charge carried by an electron, using the elegant "falling-drop method"; he also proved that this quantity was a constant for all electrons (1910), thus demonstrating the atomic structure of electricity -
Rutherford Overturned Thomson's model
Rutherford overturned Thomson's model in 1911 with his well-known gold foil experiment in which he demonstrated that the atom has a tiny, heavy nucleus. -
Period: to
Einstein's Theory of Relativity
He determined that the laws of physics are the same for all non-accelerating observers, and he showed that the speed of light within a vacuum is the same no matter the speed at which an observer travels. -
Period: to
Robert A. Millikan verified Einstein's Equation
Next, he verified experimentally Einstein's all-important photoelectric equation, and made the first direct photoelectric determination of Planck's constant h. -
The Oil Drop Experiment
While at the University of Chicago, Robert Millikan worked with one of his graduate students, Harvey Fletcher, to attempt to measure the charge of an electron. -
Bohr Hydrogen Theory
In 1913, Niels Bohr proposed a theory for the hydrogen atom based on quantum theory that energy is transferred only in certain well defined quantities. -
General Theory of Relativity
Einstein gave a series of lectures in 1915 about his new theory, which was to become known as the General Theory of Relativity, including a new equation to replace Newton's law of gravity, now known as Einstein's field equation. -
Louis de Broglie's Particle-Wave Duality
At the time, the wave and particle interpretations of light and matter were seen as being at odds with one another. He suggested that these seemingly different characteristics were instead the same behavior observed from different perspectives that particles can behave like waves, and waves can behave like particles. Broglie's theory became known as the Wave Particle Duality or the De Broglie Hypothesis Basically he suggested that all matter has wave properties. -
Uncertainty Principle
He said this means that electrons do NOT travel in neat orbits. Also, all electrons that contain photons will then change momentum and physics. -
Werner Heisenburg and The Atomic Theory
Werner Heisenberg contributed to the atomic theory by including quantum mechanics, the branch of mechanics, based on quantum theory, used for interpretating the behavior of elementary particles and atoms. -
James Chadwick Discovered Neutrons
In 1932, James Chadwick bombarded beryllium atoms with alpha particles. An unknown radiation was produced. Chadwick interpreted this radiation as being composed of particles with a neutral electrical charge and the approximate mass of a proton. This particle became known as the neutron. -
Ernest Rutherford's Death
October 19, 1937, Cambridge, United Kingdom -
JJ Thompson's Death
August 30, 1940, Cambridge, United Kingdom -
Max Planck's Death
October 4, 1947, Göttingen, Germany -
Robert Millikan's Death
December 19, 1953, San Marino, California, United States -
Albert Einstein's Death
April 18, 1955, Princeton, New Jersey, United States -
Niels Bohr's Death
November 18, 1962, Copenhagen, Denmark -
James Chadwick's Death
July 24, 1974, Cambridge, United Kingdom -
Louis de Broglie's Death
March 19, 1987, Louveciennes, France -
Werner Heisenberg and Matrix Mechanics
Using his knowledge, he created matrix mechanics, the first version of quantum mechanics in 1925
