The development of atomic theory

Democritus

400

Particle Adventure- History
Greece. BC
Thought that the universe consisted of empty space and an almost infinite number of particles which differ from each other in their position, form and arrangement. He called them atoms.

Isaac Newton

Jan 1, 1704

Particle Adventure- History
English
He experimented on the law of mechanics and stated that everything moves, big or small. He also showed this mathematically.

John Dalton

Jan 1, 1803

Wikipedia- John Dalton
English
Said that the atoms of different elements could be distinguished by their weight.

G.J. Stoney

Jan 1, 1894

Wikipedia- George Johnstone Stoney
Irish.
Proposed that there are electrons and they conduct electricity

J.J. Thomson

Jan 1, 1897

Nobel Prizes- Thomson
British.
He found that cathode rays could be deflected by an electric field. They have a small amount of negatively charged particles,.

Planck

Jan 1, 1900

Wikipedia- Max PlanckGerman.
Discovered the quantum theory also did a lot of research on heat and realised that all particles that have energy have heat.

Nagaoka

Jan 1, 1903

Wikipedia- Hantaro Nagaoka
Japanese.
Developed the structure of an atom, but was not accepted as the universal model

MIlikan

Jan 1, 1909

Wikipedia- Robert Andrews MilikanJulian Trubin- Milikan
USA
Conducted an oil drop experiment, to measure electric charge. This meant balancing the gravitational force with the electric force of the tiny droplets of oil suspended between two electric rods. After a countless droplets, and a few calculations he calculated the mass of a single electron.

E. Rutherford

Jan 1, 1911

Answers. com - Rutherford
New Zealand.
He named the nucleus and proton. Also explained radioactivity as the disintergration of atoms. Made the accepted model of the structure of an atom.

H.G.J Moseley

Jan 1, 1914

Chemistry- MoseleyLibrary thinkquest- atomic development
British
Studied the frequencies of x-rays given when electrons strike the positive side of a battery. Found that there was a realtionship between the x-rays and the atomic number of the metal. Realised that the atomic number was equal to the positive charge of an atom.

Bohr

Jan 1, 1922

Wikipedia- Neils Bohr
Danish
Bohr model of the atom shows that electrons orbit around the nucleus. Discovered that it is the electrons on the outermost shell of an atom that determines the element's characteristics.

James Chadwick

Jan 1, 1932

Nobel Prize - Physics
English
Proved the existence of neutrons. Also worked on the creation of the atomic bomb