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Democritus
Democritus was a student of Leucippus, and co-originator of the belief that all matter is made up of various imperishable indivisible elementswhich he called "atomos", from which we get the English word atom. -
John Dalton
In explaining the law of partial pressures to skeptical chemists of the day—including Humphry Davy—Dalton claimed that the forces of repulsion thought to cause pressure acted only between atoms of the same kind and that the atoms in a mixture were indeed different in weight and “complexity.”
He proceeded to calculate atomic weights from percentage compositions of compounds, using an arbitrary system to determine the likely atomic structure of each compound. If there are two elements that can com -
Dmitri Mendeleev
Mendeleev is best known for his work on the periodic table; arranging the 63 known elements into a Periodic Table based on atomic mass, which he published in Principles of Chemistry in 1869. His first Periodic Table was compiled on the basis of arranging the elements in ascending order of atomic weight and grouping them by similarity of properties. He predicted the existence and properties of new elements and pointed out accepted atomic weights that were in error. -
J.J. Thomson
In 1897 the British physicist Joseph John (J. J.) Thomson (1856–1940) discovered the electron in a series of experiments designed to study the nature of electric discharge in a high-vacuum cathode-ray tube. -
R.A. Millikan
As a scientist, Millikan made numerous momentous discoveries, chiefly in the fields of electricity, optics, and molecular physics. 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. -
Ernest Rutherford
Rutherford formulated the Rutherford model of the atom in 1911. It showed that a very small positively charged nucleus was orbited by electrons. -
Niels Bohr
1913, he passed on to a study of the structure of atoms on the basis of Rutherford's discovery of the atomic nucleus. By introducing conceptions borrowed from the Quantum Theory as established by Planck, which had gradually come to occupy a prominent position in the science of theoretical physics, he succeeded in working out and presenting a picture of atomic structure that, with later improvements (mainly as a result of Heisenberg's ideas in 1925), still fitly serves as an elucidation of the ph -
Henri Moseley
Moseley discovered a systematic mathematical relationship between the wavelengths of the X-rays produced and the atomic numbers of the metals that were used as the targets in X-ray tubes. This has become known as Moseley's law.. -
Erwin Schrodinger
Schrödinger's work in quantum theory resulted in the creation of a new scientific discipline—wave mechanics, which has as its centerpiece the Schrödinger wave equation, explained in a series of four papers published in 1926. This equation and the later relativistic versions are considered by many scientists to have the same central importance to molecular quantum mechanics as Newton's laws of motion have to large-scale classical mechanics. -
Heisenberg
Heisenberg created the Uncertainty Principle Definition which is the scientific principle stating that it is impossible to determine with perfect accuracy both the position and momentum of a particle at any given point in time. -
James Chadwick
In 1932, Chadwick discovered a previously unknown particle in the atomic nucleus.[3] This particle became known as the neutron because of its lack of electric charge.
