Contributions of Scientists to the Historical Development Atomic Concepts

John Dalton

Sep 6, 1766

British chemist and physicist John Dalton, who drew up the first list of atomic weights.Dalton's most significant work was done between 1795 and 1805, but fame came later—when the importance of his atomic theory was realized
He applied Newton's idea of small, indivisible atoms to the study of gases in the atmosphere and used it to advance a quantitative explanation of chemical composition.
http://www.chemheritage.org/discover/online-resources/chemistry-in-history/themes/the-path-to-the-perio

Tomas Young

Jun 13, 1773

he showed that his interference experiments verified the wave theory of light. Young made notable scientific contributions to the fields of vision, light, solid mechanics, energy, physiology, language, musical harmony, and Egyptology.
http://micro.magnet.fsu.edu/optics/timeline/people/young.html

Amedeo Avogadro(http://www.chemheritage.org/discover/online-resources/chemistry-in-history/themes/the-path-to-the-periodic-table/avogadro.aspx)

Aug 9, 1776

The contributions of the Italian chemist Amedeo Avogadro (1776–1856) relate to the work of two of his contemporaries, Joseph Louis Gay-Lussac and John Dalton. Gay-Lussac’s law of combining volumes (1808) stated that when two gases react, the volumes of the reactants and products—if gases—are in whole number ratios. This law tended to support Dalton’s atomic theory, but Dalton rejected Gay-Lussac’s work. Avogadro, however, saw it as the key to a better understanding of molecular constituency.

Faraday

Jan 1, 1791

Michael Faraday, the leading chemist and natural philosopher in England during the middle third of the nineteenth century, discovered the principle behind the electric motor (1821), benzene (1825), the electric transformer and generator (1831), the laws of electrolysis, and the magneto-optical effect and diamagnetism (1845), which enabled him to develop the field theory of electromagnetism üone of the cornerstones of modern physics.

http://www.fi.edu/franklin/scientst/faraday.html

Crooks

Jun 17, 1832

Discovered cathode rays had the following properties: travel in straight lines from the cathode; cause glass to fluoresce; impart a negative charge to objects they strike; are deflected by electric fields and magnets to suggest a negative charge; cause pinwheels in their path to spin indicating they have mass.

http://www.fi.edu/franklin/scientst/faraday.html

J.J Thompson

Dec 18, 1856

J. J. Thomson (1856-1940) identified the negatively charged electron in the cathode ray tube in 1897. He deduced that the electron was a component of all matter and calculated the charge to mass ratio for the electron.
http://www.nobelprize.org/nobel_prizes/physics/laureates/1906/thomson-bio.html

M.Planck

Apr 23, 1858

Planck made many contributions to theoretical physics, but his fame rests primarily on his role as originator of the quantum theory. This theory revolutionized human understanding of atomic and subatomic processes, just as Albert Einstein’s theory of relativity revolutionized the understanding of space and time. Together they constitute the fundamental theories of 20th-century physics

http://www.nobelprize.org/nobel_prizes/physics/laureates/1918/planck-bio.html

E.Rutherford

Aug 30, 1871

Ernst Rutherford (1871-1937) proposed the nuclear atom as the result of the gold-foil experiment in 1911. Rutherford proposed that all of the positive charge and all of the mass of the atom occupied a small volume at the center of the atom and that most of the volume of the atom was empty space occupied by the electrons. This was a very radical proposal that flew in the face of Newtonian Physics.

http://cstl-csm.semo.edu/mcgowan/ch181/atomhist.htm

A.Einstein

Mar 14, 1879

Einstein contributed to the atomic theory in a very important way. Instead of just theorizing that atoms may possibly exist, he actually found a way to prove that they did. He did this by using his theories in quantum physics to explain the photoelectric effect and Brownian motion, which ultimately led to solid evidence that atoms exist and even showed how atoms are structured.
http://www.ask.com/question/how-did-einstein-contribute-to-the-atomic-theory

N.Bohr

Oct 7, 1885

Niels Bohr applies quantum theory to Rutherford's atomic structure by assuming that electrons travel in stationary orbits defined by their angular momentum. This led to the calculation of possible energy levels for these orbits and the postulation that the emission of light occurs when an electron moves into a lower energy orbit
http://www.rsc.org/chemsoc/timeline/pages/1913.html

Erwin Schrödinger

Aug 12, 1887

In 1926 Erwin Schrödinger, an Austrian physicist, took the Bohr atom model one step further. Schrödinger used mathematical equations to describe the likelihood of finding an electron in a certain position. This atomic model is known as the quantum mechanical model of the atom. Unlike the Bohr model, the quantum mechanical model does not define the exact path of an electron, but rather, predicts the odds of the location of the electron.
http://www.abcte.org/files/previews/chemistry/s1_p6.html

Henry Moseley

Nov 23, 1887

Henry Moseley (1887-1915): A British chemist, Henry Moseley studied under Rutherford and brilliantly developed the application of X-ray spectra to study atomic structure; Moseley's discoveries resulted in a more accurate positioning of elements in the Periodic Table by closer determination of atomic numbers.
http://www.chemistry.co.nz/henry_moseley.htm

J. Chadwick

Oct 20, 1891

Chadwick made a fundamental discovery in the doorman of nuclear science.He proved the existence of neutrons.James predicted the atom would have a neutron.
He established that atomic number is determined by the numbers of protons in an atom.
He also discovered the fourth subatomic particle,the neutron.
James was most famous for his discovery of the neutron in an atom
http://jameschadwickatomictheory.weebly.com/

Louis de Broglie

Aug 15, 1892

In his 1924 PhD thesis he postulated the wave nature of electrons and suggested that all matter has wave properties. This concept is known as wave-particle duality or the de Broglie hypothesis. He won the Nobel Prize for Physics in 1929
www.nobelprize.org

Heisenberg

Dec 5, 1901

ın 1927 he published his uncertaınty prıncıble he was awarded noble prıze ın physıcs for the creation of quantum mechanics.The idea of circular orbits and knowing where the electron is located is impossible. He also made ımportant contributions to the theories of the atomic nucleus and subatomic particles.