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Period: 480 BCE to
Alchemists
Alchemy began as far back as Aristotle and his theory of everything being earth, fire, air, water. It played a big role, not only as it helped discover and lead to the atom, but it played roles in medicine, discovery of gunpowder and other world changing discoveries. Alchemists believed you could transmute base metals into precious metals using the philosophers stone, Alexander the great studied alchemy under Aristotle. -
Period: 384 BCE to 422 BCE
Aristotle
Aristotle lived between 384- 422 B.C. Aristotle looked deeper when people began questioning objects and how they were made. He found that there were four causes; the first cause is the Material Cause in which said what stuff is made from. Second cause: The efficient marker of things. Third Cause: Formal which is the pattern. Forth Cause: The purpose that something is made.
He thought that everything had a goal. Aristotle was a smart man yet some of hid ideas have already been disproven -
Period: 460 to 370 BCE
Democritus
He thought that every basic element is made up of matter which is in turn made up of atoms. He thought that atoms were “uncuttable” or indivisible. He would state this theory to others but nobody believed him since he wasn’t Aristotle. He would try to find a way to show how motion and change will still occur while maintaining the unity of the physical world. He originally called atoms "atomos" which meant indivisible. -
Charles-Augustin de Coulomb
Charles-Augustin de Coulomb won accolades for his work in torsion balances after studying engineering and plied his trade with the military. He offered pioneering theories in the force found between electrical charges, as well as magnetic attraction and repulsion. The unit of measurement known as the coulomb is named in his honor. -
Period: to
Joseph Proust
He made up the theory of the Law of Definite Proportions. This theory states that any given chemical compounds always contain the same elements are the exact same as when they come out of a reaction. This is how we got out chemical reaction equations. He came to discover the law, in 1794, by experimenting on sulfuric hydrogen. He would help guide Dalton to create the Law of Multiple Proportions and ultimately his Atomic Theory. -
Period: to
Antoine Lavoisier
Invented the law of conservation of mass. This is the law that the mass of the reactants are the same as the products. For example, two reactants, both with a mass of 2g, will create a product of 4g. Matter can not be created nor destroyed. -
Period: to
Michael Faraday
Faraday is an English scientist that contributed to the Atomic theory by his studies of electromagnetism and electrochemistry. His theory over electromagnetics was that magnetism can affect the rays of light. One of his many accomplishments was of when he created the base of electric motor technology. The S1 unit of capacitance, the farad, is named after Faraday. Specifically involved with the study of chlorine, he discovered to major compounds called chlorine and carbon. -
Period: to
John Dalton
John Dalton was a chemist who is credited with pioneering modern atomic theory. Also, he was the first to study color blindness. He was the first scientist to explain the behavior of atoms in terms of the measurement of weight. In 1803, he revealed the the concept of Dalton’s Law of Partial Pressures. Dalton identified the hereditary nature of red-green color blindness during his early career. -
Period: to
Antoine Henri Becquerel
He was most famous for when he got a Nobel Peace Prize for his discovery on the Uranium Atom. He did an experiment with uranium salts where he found they emitted a type of ray, similar to an x-ray. The led him to discover that uranium's rays could be deflected using magnetic or electric fields. Antoine only received half a nobel prize for his discovery, Marie Curie received the other half. -
Period: to
William Crookes
His invention brought the focus towards the subatomic structure of the atom. He experimented and created the Crookes tube. During his career, his tube is a cathode-ray tube which is when the electrons are generated by a glow discharge in a low-pressure gas. -
Period: to
Max Planck
Max Planck was a German theoretical physicist who lived in Germany. Planck originated the Quantum Theory, a theory that revolutionized our understanding of atomic and subatomic processes. Creating this theory won him the Nobel Prize for physics in 1918.
Max Planck forced humankind to revise some of the most cherished philosophical beliefs, along with Albert Einstein. Both Einstein and Planck constituted the fundamental theories of 20-century physics. -
Period: to
Fredrick Soddy
He evolved the "displacement law", namely that emission of an alpha-particle from an element causes that element to move back two places in the Periodic Table. His peak was in 1913 with his formulation of the concept of isotopes, which stated that certain elements exist in two or more forms which have different atomic weights but which are indistinguishable chemically. Soddy's discoveries founded the fledging science of Nuclear Chemistry. His ideas of atomic structure have contributed greatly. -
Period: to
Lise Meitner
Meitner discovered nuclear fission and gave the first theoretical explanation of the fission process. She was mainly interested in physics, and became a chemist. Her research was used to help Hahn and Strassman find the proof of fission. -
Period: to
J.J. Thomson
With using the idea of electricity transmitting by a tiny particle related to the atom, he estimated its magnitude by experimenting with a charged particles in gases. He also showed that cathode rays consists of the particles that conduct the electricity. Concluded he also found out that electrons are part of atoms. -
W.K. Roentgen
Discovered x-ray. He was studying electrical current through a low pressured gas to learn more on Cathode rays. He found that, if the discharge tube is enclosed in a sealed, thick black carton to exclude all light, the path of the rays became fluorescent. During subsequent experiments he found that objects of different thicknesses interposed in the path of the rays showed variable transparency. Roentgen showed that the rays were shown by the impact of cathode rays on an object. -
Period: to
Paul Villard
His Studies of cathode ray, x rays, and radium rays. His experiment in radio activity led to the unexpected discovery of a third kind of radiation, the gamma rays. The gamma rays were similar to x rays or light because of form of electromagnetic radiation. The difference between them is the gamma rays have shorter wavelengths. -
Marie & Pierre Curie
Pierre and Marie Curie are best known for their pioneering work in the study of radioactivity, which led to their discovery in 1898 of the elements radium and polonium. -
Period: to
Enrico Fermi
His work led to the discovery of slow neutrons, which led to the discovery of nuclear fission and the production of elements lying beyond what was until then the Periodic Table.In 1938, Fermi was without doubt the greatest expert on neutrons. He developed a theory,according to which a universal magnetic field would account for the fantastic energies present in the cosmic ray particles. The Nobel Prize for Physics was awarded to Fermi for his work. Known as the architect of the nuclear age. -
Period: to
Fritz Strassman
German physical chemist who discovered neutron-induced nuclear fission in uranium and he opened the field of atomic energy. He joined Lise Meitner to to investigate the radioactive products formed when uranium is bombarded by neutrons. He split the uranium atom into two lighter atoms. -
Period: to
Albert Einstein
He became famous for the theory of relativity, which laid the basis for the release of atomic energy. In 1905 Albert Einstein formulates Special Theory of Relativity. Einstein calculates how the movement of molecules in a liquid can cause the Brownian motion. -
Period: to
Robert Millikan
He has created huge accomplishments in the areas of atomic theory and electric charge. During his career, his most famous scientific work was the oil drop experiment. The reason why it was called this was because the experiment simply dropped oil between electrodes, which charged the plates electrically. This showed his theory of a negative charged particle within an atom. -
Period: to
Hans Geiger
Co-invented the Geiger Counter.
He began working on the counter in 1907 with Walther Müller and finished in 1911. States that a linear relationship exists between the logarithm of the range of alpha-particles and the radiative time constant, which is involved in the rate of decay of emitting nuclei.
A radiation detector consisting of two electrodes with a low-pressure gas in between.Geiger counters can count radiation but cannot distinguish either the energy or kind of radiation. -
Period: to
Ernest Rutherford
He was the first to discover that atoms have a small charged nucleus surrounded by largely empty space, and are circled by tiny electrons, which became known as the Rutherford model (or planetary model) of the atom. He is also credited with the discovery of the proton in 1919, and hypothesized the existence of the neutron. -
Niels Bohr
Contributed to finding out more about the atomic structure and worked with other scientists to create the quantum theory. He won the 1922 nobel prize from his achievements. He proposed a theory for the hydrogen atom based on quantum theory that energy is only transferred in certain well defined quantities. Electrons should move around the nucleus but only in prescribed orbits. -
Period: to
Philip Abelson
Abelson helped was a physicist from America whose discoveries helped gather uranium that is necessary to build an atomic bomb. In his first years as a physicist, he developed a liquid thermal diffusion process for uranium 235-isotopes. Moving to the U.S. Naval Research Laboratory in Washington D.C., he began his beginning work on thermal diffusion pilot plant. Abelson's accomplishment resulted in America having enough uranium to create their first atomic bomb called "Little Boy". -
Period: to
Erwin Schrödinger
He was an Austrian physicist in 1926, advanced the Bohr atom model a little more. He used equations to describe the chances of finding an electron in a certain place. This model is known as the quantum mechanical model of the atom, and the quantum mechanical model does not define the exact path of an electron, but rather, predicts the odds of the location of the electron. -
Period: to
James Chadwick
In 1932, from February to May, Chadwick was working toward his discovery of a neutron. This discovery contributed to the later discovery of nuclear fission, it which went on to the development of the atomic bomb, and, by having knowledge of the neutron, a more accurate model of the atom was constructed. -
Period: to
Frederic and Irene Curie
They discovered that radioactive elements can be produced artificially from stable elements. They did this by exposing aluminum foil to alpha particles, however, when they removed the alpha particles, the aluminum foil was still radioactive. This expanded what scientists thought they could do, and after they learned they could do this, other elements were turned radioactive, and they were used to make medications and other things. -
Period: to
Otto Frisch
While he was working with Otto Stern, Frisch produced work on the diffraction of atoms. He found that the magnetic moment of the proton was much larger than what had been previously believed. He also, with his aunt Lise Meitner, hypothesized that the uranium nucleus was split in two, and they coined the name “fission” -
Otto Hahn
Hahn’s most memorable discovery. While working with Fritz Strassmann, Hahn discovered nuclear fission during an experiment in which a uranium atom split into barium. This led to him winning the Nobel Prize in Chemistry "for his discovery of the fission of heavy atomic nuclei." in 1944. -
Edward McMillan
In 1940 McMillan and Phillip Abelson produced a new element, element 93, when they bombarded uranium-235 with neutrons. This was the first time a transuranium element had ever been artificially created. McMillan dubbed the new element "neptunium." He also helped to produce plutonium-239 by bombarding uranium-235 with deuterons. -
Joseph Kennedy
Kennedy discovered plutonium with Edwin McMillan, Glenn Seaborg, and Arthur Wahl. Kennedy was the man that built the instruments that proved that plutonium existed. Kennedy, Seaborg, and Wahl also found that plutonium was fissile. This discovery was vital for the Manhattan Project research. -
Period: to
Glenn T. Seaborg
He first collaborated with 3 other scientists to isolate plutonium, then he did it again on his own, this time isolating Uranium. Doing so, he established thorium’s nuclear fuel potential. He later discovered the first 8 transuranium elements and it was called “one of the most significant changes to the periodic table since Mendeleev.” -
Arthur Wahl
After getting his degree in radiochemistry, in February of 1941 he helped discover and isolate the radioactive isotope plutonium with a team of scientists, including Glenn Seaborg, at University of California, in Berkeley. These same scientists also discovered that plutonium could be used as a weapon. -
Period: to
George Zweig
In 1964, Zweig recognized the existence of the subatomic particles that were later named quarks. He originally called his model of quarks “aces” and although his naming did not stick, his research provided information and he also contributed the knowledge of the electrical charges being equal to ⅓ or ⅔ of an electron or proton. -
Murray Gell-Mann
Hypothesized that quarks are the fundamental particles that make up all known subatomic particles except leptons.