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400
Alchemists
Alchemy's roots can be drawn all the way back to metallurgy's beginning in 3500 BCE; however, most alchemy ranges from Greek-Roman times to the 18th century, existing in Greco-Roman Egypt. the Islamic world, Medieval Europe, the Renaissance, India, and China. Its main goals have been the creation of the philosopher's stone, which could turn basic metals into noble metals and the creation of an elixir of life. Its practices relate to mythology, magic, religion, and spirituallity. -
400
Alchemists (continued)
Alchemists believed in the idea of transmutation, where one could turn one object or element into another. Alchemy overall is recognized as a protoscience and has indeed had contributions to chemistry and medicine. The structure of some basic lab techniques and theories, terminology, and experimental methods have been developed by alchemists. -
460
Democritus of Adbera
Democritus of Adbera (circa 460 BCE - 370 BCE) created is own atomic theory in 465 BCE based on the following ideas:
1)All matter was made up of atoms.
2)Atoms were always in motion.
3)Atoms were solid but invisible and indestructible.
4)Atoms have different sizes, shapes, and masses for different elements ,but atoms of the same element are always the same.
Although his Atomic Theory is very close to the theory of today, not many people believed him. -
Benjamin Franklin
Benjamin Franklin (1706-1790) ,by flying a kite during a storm in 1752, developed the idea that matter had charges. These charges can be positive or negative. Also in 1750, Franklin was able to measure the size of a single molecule. -
Antoine Lavoisier
Antoine Lavoisier (1743-1794) proposed the Combustion Theory in 1777 and the Law of Conservation of Mass in 1774. The Combustion of Theory disproved the theory of phlogiston that was held back then. Because Lavoisier worked by burning substances so often, he was able to name oxygen. -
Joseph Proust
Joesph Proust (1754-1826) first proposed the Law of Constant Composition in 1794, which said that a compound is composed of the exact same proportions of each element, no matter how it was formed. -
John Dalton
John Dalton (1766-1844) proposed the Atomic Theory in 1803. His theory included the ideas listed:
1)Pure elements consisted of particle called atoms.
2)Atoms of one element are always the same for that element.
3)Atoms of different elements can be differentiated by their atomic weights.
4)Atoms combine to form chemical compounds.
5)Atoms cannot be created or destroyed. -
J.J Berzelius
Jöns Jacob Berzelius (1779-1848) is credited with coming up with the atomic symbols we used today and for the determination of the atomic weights as well. -
Michael Faraday
In 1832, Michael (22 September 1791 – 25 August 1867) studried electricity's effect on solutions. He created the term electrolysis to stand for the splitting of molecules with electricity. In addition, he developed the laws of electrolysis. -
William Crookes
In 1897, William (17 June 1832 – 4 April 1919) discovered several cathode ray properties, including how, beginning at the cathode, they travel in straight lines to the anode; they have the ability to make glass fluoresce; with a negative charge, they can impact objects they strike; they can be deflected by both electrical fields and/or magnets (this suggests a negative charge); and they can affect pinwheels by causing them to spin (meaning that the cathode rays have a mass). -
Dmitri Mendeleev
In 1869, Dimitri (8 February 1834 – 2 February 1907) arranged all the elements known during his time into 7 groups. Each group had similar properties, for he discovered the notion that element properties were related periodically to their atomic weight. This idea is known as the Periodic Law. -
Henry Becquerel
Henry Becquerel (1852-1908) discovered radiation in 1896 when unexposed photographic plates developed a clear image because of the potassium uranyl sulfate on top of this. This experience won him the Nobel Prize in 1903 along with Marie and Pierre Curie. -
Joseph John Thomson
In 1897, Joseph (18 December 1856 – 30 August 1940) determined the charge : mass ratio of an electron. This was done using a CRT and he discovered the ratio to be 1.759 x 10 8 coulombs/gram. The same year, he studied canal rays. During his study, he discovered the rays were associated with the proton H+. -
Max Planck
Max (April 23, 1858 – October 4, 1947) in 1900 explained the concept of hot glowind matter by using the quanta idea (quanta are discrete units of energy). -
Marie & Pierre Curie
Marie Curie (7 November 1867 – 4 July 1934) formed the term radioactivity as the name of the decay process of uranium and thorium (the two elements she was studying). She and Pierre (15 May 1859 – 19 April 1906) later in 1898 discovered polonium and radium (radioactive elements). -
Robert Millikan
Robert (March 22, 1868 – December 19, 1953), in 1909, used his oil drop experiment, conducted at the University of Chicago, to determine the charge of the electron. He determined that the charge was e = 1.60 x 10-19 coulombs” -
Ernest Rutherford
In 1898, Ernest Rutherford (30 August 1871 – 19 October 1937) studied uranium and thorium radiation and called them alpha and beta (the radiations). Later in 1911, he shot alpha particles at high speeds at a thin peice of gold foil. Using the results, he came to the conclusion that the nucleus was extremely dense, small, and positive in charge. In addition, he also concluded that electrons are around and not inside the nucleus. -
Francis Aston
Fransic Aston (1877-1945) invented the mass spectrograph so he was able to observe isotopes, and for his work in 1920, he was awarded the Nobel Prize in 1922 for Chemistry. -
Albert Einstein
In 1905, Einstein (14 March 1879 – 18 April 1955) published the E=mc^2 equation. In 1921, he received the Nobel Prize in Physics for work on theoretical physics and the law of the photoelectric effect He published the general theory of relativity in 1916, which a year later he applied to a structure of the universe. He created explanations of particle theory and molecular motion. In addition, he studiedthe thermal properties of light. Overall, he published more than 300 scientific papers. -
Hans Wilhelm Geiger
Hans Wilhelm Geiger (1882-1945) worked with Marsden in the "gold foil experiment" when they discovered more about the structure of the atom. In addition, he also developed the Geiger counter that is able to measure radiation(1928). The Geiger counter is able to detect alpha, beta, and ionizing radiation. -
Niels Bohr
Niels Bohr (1885-1962) created an atomic model where the electrons moved around a positively charged nucleus, and he also found that the electrons traveled in orbits around the nucleus(called the "planetary model"). He also found out that the substance's chemical properties were dependant on the amount of electrons in the outer orbit. Bohr was honored for his work in 1922 with a Noble Prize. -
Erwin Schrödinger
In 1926, Erwin (12 August 1887 – 4 January 1961) had several discoveries in the field of quantum theory. His discoveries formed the foundation of wave mechanics. He then formed the wave equation (both the stationary and the time-dependent Schrödinger equation). It was presented in 1926. Later that year, he gave an interpretation its physical meaning. In addition, He worked on color, color perception, and colorimetry (Farbenmetrik) and even published three papers on such topics in 1920. -
Henry Moseley
Henry Moseley (1887-1915) developed the idea of the atomic number, and he also rearranged the periodic table accoring to atomic number rather than atomic mass. -
James Chadwick
James Chadwick (1891-1974) discovered the neutron in 1932. He also worked with Rutherford in studing the properties and structure of the nucleus. -
Louis deBroglie
Louis deBroglie (1892-1987) developed many ideas that are now used in the Theory of Wave Mechanics. He believed that electrons could act like waves and particles, which is why they can have properties for both. -
Werner Heisenberg
Werner Heisenberg (1901-1976) proposed the Principle of Indeterminancy in 1927, and it states that the position and velocity of a particle cannot be known simultaneously. -
Paul Dirac
Paul Dirac (1902-1984) created the Dirac Equation that predicts the existence of antimatter. Antimatter is are antiparticles that have the same mass as other particles but opposite cahrges. -
Aristotle
Aristotle (circa 384-322 BCE)believed that there were 4 elements. They were air, fire, water, and earth. He did not believe in atoms, and he thought that no matter how small you cut a substance up, it would always remain that same substance. Since, Aristotle was more popular than other thinkers at his time, his theory was believed for more that 2000 years. -
Period: to
Atomic Timeline
