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Jan 1, 660
Democritus
Adopted the Atomic Theory, which stated that the universe consists of things smaller than the human eye can observe, The universe is composed of two elements: The atoms and the void in which they move. -
Antoine Lavoiser
Discovered that respiration was a process of combustion, with the utilisation of oxygen and the production of carbon dioxide, used findings to promote public health. He wrote the first extensive list of elements, and helped to reform chemical nomenclature. -
Joseph Louis Proust
Proposed Law of Definite Proportions, which states that in any compound the elements are presenti n a feixed proportion by weight. Ratio of Elements will never change regardless of masses -
Indivisible Solid Sphere Model
Devloped by John Dalton, declared that atoms were responsible for making up all matter,atoms join to form compounds, that within the same mass, all atoms are identical and that atoms are indivisible. -
John Dalton
Established Daltons Atomic Theory. -
All matter is made of atoms, atoms are indivisible and indestructible.
All atoms of a given element are identical in mass and properties
Compounds are formed by a combination of two or more different kinds of atoms.
A chemical reaction is a rearrangement of atoms. -
Michael Faraday
Studied effect of electricity of solutions discovered electrolysis as the method of splitting molecules using electricity in 1832 Made law of electrolysis based on studies -
Henri Becquerel
Studied effect of x-rays on film and phosphorescence Discovered some chemicals spontaneously decompose and give off very penetrating rays -
J.J Thompson
Discovered Electron while expirmenting with a Crooke's or Cathode ray, tube.
Demonstrated Cathode rays were negatively charged
Later proved incorrect by student, -
Marie and Pierre Curie
In 1898, they discovered Polonium and Radium. Had pioneerning work in the study of radioactivity Marie= Mother of atomic physics -
Max Planck
Wokred in thermodynamics to help formulate theories
Originator of Quantum Theory, which revolutionized our understanding of atomic and subatomic processes, just as Albert Einstein’s theory of relativity revolutionized our understanding of space and time. -
Plum Pudding Model
Was proposed by JJ Thomson in 1904, used cathode rays -
Albert Einstein
Discovered equation E=MC2, which showed amount of energy stored in a certain amount of matter Established theory of relativity Dissaproved of the idea of quantum mechanics and was against many of Bohr's theories. -
Ernest Rutherford
Used gold foil expirement to discover the nucleus of an atom
Discovered that there was a positively charged central core to an atom called nucleus -
Niels Bohr
Danish Physicist, Made substantial contributions to quantum theory
Worked in prominent team of physicists on the Manhattan project
Proposed theory for hydrogen atom based on quantum theory that energy is transferred only in certain well defined quantities. -
Planetary Model
Began by Rutherford and Improved by Bohr (Rutherford Bohr Model) Bohr Model introduced in 1913, depicts the atom as a small, positively charged nucleus surrounded by electrons the travel in circular orbits around the nucleus, similar to the structre of the solar system, but with attraction provided by electrostatic forces rather than gravity -
Lisa Meitner
Became first to recognize that the uranium atom, when bombarded by neutrons, actually split. discovered 1st long lived isotope of the element protactinium. Was also part of team that first discovered nuclear fission -
Robert Milikan
Worked on oil drop expirement where he measured and later determined the charge of a single electron.
Millikan was able to show that the charge on a drop was always an integral multiple of a small, but finite value -
Electron Cloud Model
Erwin Schrödinger and Werner Heisenberg. (Schrodinger)
This atomic model does not specifically pinpoint where an electron is likely to be as the Bohr model does. Instead, it depicts all the positions where an electron might be, which generates a cloud of possible locations that gets denser as it approaches the nucleus. -
Erwin Schrodinger
Schrödinger used mathematical equations to describe the likelihood of finding an electron in a certain position.
(Established quantum mechanical model)
Predicts odds of location of electron -
Quantum Mechanical Model
Fundamental equation developed in 1926 by Erwin Schrödinger that established the mathematics of quantum mecha of the wave function that describes the wavelike properties of a subatomic system. -
Louis Debroglie
Introduced Wave Mechanics Theory, where he believed that electrons act both like particles and waves just like light
Discovered electrons act like waves
1929 nobel peace prize -
James Chadwick
Chadwick discovered the neutron and that neutrons help stabilize the protons in the atom's nucleus. Because the nucleus is so tightly packed together, the positively charged protons would tend to repel each other normally. Led British team in the Manhattan project -
Otto Hahn
Father of Nuclear Chemistry worked to discover radioactive elements such as thorium, as well as recognizing uranium aton in 1938. Discoveries later used in nuclear fission -
Glen T. Seaborg
American Nuclear Chemist Best known for isolating and identifying transuranium elements (elements heavier than uranium) Discovered ten transuranium elements, one being seaborgium. -
Aristotle
Aristotle believed that the materials of earth were not made of atoms, but were made of the 4 elements (Earth, wind, fire and water) Caused Demicritus's theory to be overlooked for almost 2,000 years.
