History of the Atomic Structure

Information from timeline taken from http://www.barcodesinc.com/articles/timeline-on-atomic-structure.htm

Main

Ancient Atomic Theory

400 BC

Democritus’ atomic theory posited that all matter is made up small indestructible units he called atoms.

http://abyss.uoregon.edu/~js/21st_century_science/lectures/lec05.html

Issac Newton

1704

Isaac Newton theorized a mechanical universe with small, solid masses in motion.

http://galileo.phys.virginia.edu/classes/252/atoms.html

Dalton's Atomic Theory

1803

John Dalton proposed that elements consisted of atoms that were identical and had the same mass and that compounds were atoms from different elements combined together.

http://dl.clackamas.edu/ch104-04/dalton%27s.htm

Faraday's Laws

1832

Michael Faraday developed the two laws of electrochemistry:
1. The mass of substance produced is proportional to the quantity of electricity.
2. A given quantity of electricity produces fewer moles of substances with higher oxidation numbers.

CliffsNotes.com. Faraday's Laws.
http://www.cliffsnotes.com/study_guide/topicArticleId-276493,articleId-276471.html

Cathode-ray Tubes

1858

Julius Plücker built one of the first cathode-ray tubes.

http://www4.nau.edu/microanalysis/Microprobe-SEM/History.html

Periodic Table

1869

Dmitri Mendeleev created the periodic table.

http://www.woodrow.org/teachers/ci/1992/Mendeleev.html

Electromagnetism

1873

James Clerk Maxwell proposed the theory of electromagnetism and made the connection between light and electromagnetic waves.

http://www.geog.ucsb.edu/~jeff/115a/history/jamesclarkemaxwell.html

Electrons

1874

G.J. Stoney theorized that electricity was comprised of negative particles he called electrons.

http://www.chemteam.info/Chem-History/Stoney-1894.html

Cathode Rays are Negative

1879

Sir William Crookes’ experiments with cathode-ray tubes led him to confirm the work of earlier scientists by definitively demonstrating that cathode-rays have a negative charge.

http://chemed.chem.purdue.edu/genchem/history/electron.html

Canal Rays = Proton?

1885

Eugene Goldstein discovered canal rays, which have a positive charge equal to an electron, later called Proton.

http://www.columbia.edu/itc/chemistry/chem-c2507/navbar/chemhist.html

Radiation... on film?

1896

Henri Becquerel discovered radiation by studying the effects of x-rays on photographic film.

http://www.physics.isu.edu/radinf/cuire.htm

Charge is related to Mass

1897

The Curies

1898

Marie Sklodowska Curie discovered radium and polonium and coined the term radioactivity after studying the decay process of uranium and thorium.

http://www.staff.amu.edu.pl/~zbzw/ph/sci/msc.htm

Alpha, Beta, Gamma

1898

Ernest Rutherford discovered alpha, beta, and gamma rays in radiation.

http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1908/rutherford-bio.html

Quantization according to Planck (not Plank)

1900

Max Planck proposed the idea of quantization to explain how a hot, glowing object emitted light.

http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch6/bohr.php

Inert is Stable

1904

Richard Abegg found that inert gases have a “stable electron configuration.”

http://www.chemistry.mtu.edu/~pcharles/SCIHISTORY/08nuclearatom.html

Saturn as an Atom

1904

Hantaro Nagaoka proposed an atomic model called the Saturnian Model to describe the structure of an atom.

http://philsci-archive.pitt.edu/4232/1/Atomic_Modeling_101208.pdf

Geiger Counter

1911

Hans Geiger invented a device that could detect alpha particles.

http://global.britannica.com/EBchecked/topic/227810/Hans-Geiger

The Isotope

1913

Frederick Soddy came up with the term "isotope" to explain the unintentional breakdown of radioactive elements.

http://abyss.uoregon.edu/~js/glossary/isotope.html

Help with the Table

1914

H.G.J. Moseley discovered that the number of protons in an element determines its atomic number.

http://www.chemistry.co.nz/henry_moseley.htm

Mass Spectrograph

1919

Francis William Aston invents the mass spectrograph, capable of separating isotopes by measuring the minute differences in their masses. He successfully identified 212 existing isotopes.

http://www.nuclearfiles.org/menu/library/biographies/bio_aston-francis.htm

Bohr's Model

1922

Niels Bohr proposed an atomic structure theory that stated the outer orbit of an atom could hold more electrons than the inner orbit.

http://www.cord.edu/faculty/ulnessd/legacy/fall2000/pfeifer/nielsbohr.htm

Electrons are like waves

1924

Louis de Broglie proposed that electrons have a wave/particle duality.

Freudenrich, Ph.D., Craig. "How Atoms Work" 01 February 2001. HowStuffWorks.com. http://science.howstuffworks.com/atom.htm

Antimatter

1928

Paul Adrien Maurice Dirac begins the modern theory of Antimatter with a paper called "The Quantum Theory of the Electron".

http://rspa.royalsocietypublishing.org/content/117/778/610

Alpha Particles

1932

Cockcroft / Walton created the first nuclear reaction, producing alpha particles

http://homepage.eircom.net/~louiseboylan/Pages/Cockroft_walton.htm

Hello, Neutron

1932

James Chadwick discovered neutrons, particles whose mass was close to that of a proton.

http://www.chemistryexplained.com/Ce-Co/Chadwick-James.html

Fission

1938

Lise Meitner, Otto Hahn, and Fritz Strassman discovered nuclear fission.

http://www.sdsc.edu/ScienceWomen/meitner.html

Transuraniums

1944 - 1958

Glenn Seaborg discovered eight transuranium elements.

http://www.osti.gov/accomplishments/seaborg.html