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Democritus
first idea of the atom -
Antoine lavoister
He 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. -
John Dalton
Democritus first suggested the existence of the atom but it took almost two millennia before the atom was placed on a solid foothold as a fundamental chemical object by John Dalton. Although two centuries old, Dalton's atomic theory remains valid in modern chemical thought.
1) All matter is made of atoms. Atoms are indivisible and indestructible. 2) All atoms of a given element are identical in mass and properties 3) Compounds are formed by a combination of two or more different kinds of atoms -
Dmitri Mendeleeve
published The Principles of Chemistry in 1869. Not only did this textbook become popular in Russia, it was later translated in English, French and German. He wrote the names of the 65 known elements on cards He then wrote the fundamental properties of every element on its own card, including atomic weight. “In a dream I saw a table where all the elements fell into place as required. Awakening, I immediately wrote it down on a piece of paper.” 2 weeks later he published the periodic table. -
Eugen Goldstein
He was an early investigator of discharge tubes, the discoverer of anode rays, and is sometimes credited with the discovery of the proton -
J.J Thomson
discovered the electron in a series of experiments designed to study the nature of electric discharge in a high-vacuum cathode-ray tube, an area being investigated by numerous scientists at the time. Thomson interpreted the deflection of the rays by electrically charged plates and magnets as evidence of “bodies much smaller than atoms” that he calculated as having a very large value for the charge-to-mass ratio. Later he estimated the value of the charge itself. In 1904 Thomson suggested a model -
Robert Millikon
Oil Drop experiment determined the size of the charge on an electron. He also determined that there was a smallest 'unit' charge, or that charge is 'quantized'. He received the Nobel Prize for his work -
Eatnest Rutherford
discovered alpha and beta rays, set forth the laws of radioactive decay, and identified alpha particles as helium nuclei. -
Henry Moseley
Moseley's contribution to the science of physics was the justification from physical laws of the previous empirical and chemical concept of the atomic number. -
Niels Bohr
proposed a model for the hydrogen atom that was consistent with Rutherford's model and also explained the spectrum of the hydrogen atom -
Max Planck
discovered the quantum theroy; a theory of matter and energy based on the concept of quanta, especially quantum mechanics. -
Erwin Schrödinger
A powerful model of the atom was developed by Erwin Schrodinger in 1926. Schrodinger combined the equations for the behavior of waves with the de Broglie equation to generate a mathematical model for the distribution of electrons in an atom. The advantage of this model is that it consists of mathematical equations known as wave functions that satisfy the requirements placed on the behavior of electrons. The disadvantage is that it is difficult to imagine a physical model of electrons as waves. -
James Chadwick
used scattering data to calculate the mass of this neutral particle. Assuming that the neutron mass was close to that of the proton, Chadwick bombarded hydrogen atoms with his produced neutrons to learn the speed of the protons after the collisions. -
Werner Heisenberg
He is best known as a founder of quantum mechanics, the new physics of the atomic world, and especially for the uncertainty principle in quantum theory.
