Upload
printdesk-by-dan
View
219
Download
0
Embed Size (px)
Citation preview
7/29/2019 Timeline of Atomic Theories
1/2
TIMELINE OF ATOMIC THEORIESDemocritus Greeks concept of matter(460 - 370):
- Matter is discontinuous. It is made up of particlescalled atoms. The properties of the atoms
determine the properties of matter.
Daltons atomic theory (1804):
- Atoms are indivisible and indestructible. They donot change during chemical reaction.
Cathode ray experiments (1879 - 1897):
- Cathode rays are made up of negative particlescalled electron.
Thomsons plum pudding model (1891):
- An atom is a positive ball of electricity withnegative electrons embedded.
Albert Einstein photon theory of light (1905):
- Light wave carries energy equal to h v, consists ofquanta or corpuscles called photon.
Rutherfords gold fat experiment 1908 - 09):
- the atom is mostly empty space. Its mass isconcentrated in the nucleus. (Nuclear Model)
Niels Bohrs atomic model (1913):
-
the atom is like a solar system. Its mass isconcentrated in the nucleus in circular orbits.
7/29/2019 Timeline of Atomic Theories
2/2
Moseleys x-ray experiments (1913):
- all atoms of one elements have the same or fixednumber of protons.
De Broglies particle-wave concept of the electron
(1924):- the electron has both particle and wave
properties.
Werner Heisenbergs Uncertainty principle (1927):
- it is not possible to define accurately the positionand momentum (velocity) of particles of atomic
dimensions, e.g., electron.
Clinton Davisson and Lester Germer (1927):- Showed an electron beam impinging on a nickel
crystal exhibits properties of diffraction and
refraction.
- Confirmed de Brogiles particle wave concept ofthe electron.
Erwin Schroedingers Wave model (1928):
- Described the wave like motion of the electronwith relevant wave equation.
James Chadwick (1932):
- Identified the neutron as the particle producedalong with carbon when beryllium is bombarded
with alpha particles.
M. Gell-Man and G, Zweig Quark (1963):
- Assumed that Quarks are even morefundamental particles than neutrons and
protons.
- The fundamental particles of matter are quarksand leptons.