History of Atomic Theory Project

Democritus

470

Democritus
Democritus was born in 470 BC and died in 360 BC. He discovered atoms. He was the first person to create an Atomic Theory. He said atoms are infinite in number and are always moving.

John Dalton

Sep 6, 1766

John Dalton
John Dalton was born on September 6,1766 and died on July 26, 1844. He believed all matter is made of atoms. He thought that all atoms are identical in mass. Atoms cannot be created nor destroyed.

J.J Thomson

Dec 18, 1856

http://www.biography.com/people/jj-thomson-40039
Thomson caled the negative particles Electrons. He also experimented a machine called the Cathode Ray Tube

Max Planc

Apr 23, 1858

http://www.groups.dcs.stand.ac.uk/~history/Mathematicians/Planck.html
Planc initiated the study of quantum mechanics when he announced in 1900 his theoretical research into the radiation and absorption.

Ernest Rutherford

Aug 31, 1871

http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1908/rutherford-facts.html Ernest used thin gold foil and alpha particles to determine two things. The postive charge was located in the center of the atom. Most of the Atom was empty space

Francis Aston

Sep 1, 1877

http://humantouchofchemistry.com/francis-aston.htm Aston invented a mass spectrograph, an instrument that used electromagnetic focussing to separate the isotopes.

Niels Bohr

Oct 7, 1885

http://www.nobelprize.org/nobel_prizes/physics/laureates/1922/bohr-facts.html Niels proposed a theory for the hydrogen atom based on quantum theory that energy is transferred only in certain well defined quantities.

Erwin Schrodinger

Aug 12, 1887

http://www.nobelprize.org/nobel_prizes/physics/laureates/1933/schrodinger-facts.html
Bohr's theory of the atom the electrons absorb and radiation of fixed wavelengths when jumping between fixed orbits around a nucleus.

James Chadwick

Oct 20, 1891

http://www.nobelprize.org/nobel_prizes/physics/laureates/1935/chadwick-bio.html James found evidence of another nuclear called Nuetron. Chadwick has had many papers published on the topic of radioactivity and connected problems.

Louis de Broglie

Aug 15, 1892

http://atomictimeline.net/index.php Louis de Broglie discovered that electrons had a dual nature-similar to both particles and waves

Werner Hiesenberg

Dec 5, 1901

http://atomictimeline.net/index.php Werner described atoms by means of formula connected to the frequencies of spectral lines.

Paul Dirac

Aug 8, 1902

http://atomictimeline.net/index.php Paul Dirac proposed anti-particles