atomic theroy

democritus

460

democritushe came up with a theory which stated that all objects are made up of little indestructible and indivisible things called atoms. although his discovery was often questioned because he could not explain the chemical side of his idea

john dalton

Sep 6, 1776

dalton johnhe proposed another theroy that all matter was composed of small indivisible particles termed atoms, atoms of a given element possess unique characteristics and weight, and three types of atoms exist

ernest rutherford

Aug 30, 1871

ernest rutheford ernest's atomic theory describing the atom as having a central positive nucleus surrounded by negative orbiting electrons

francis aston

Sep 1, 1877

francis astonhe discovered isotopes. by his invention of the mass spectrograph, an apparatus in which the ingenious use of electromagnetic focusing enabled him to utilize the very slight differences in mass of the two isotopes to effect their separation.

niels bohr

Oct 7, 1885

neils bohr he is best known for his theory of the Hydrogen atom and he used Planck's concept of quantization.he said that the electron could only have certain energies and light emitted from Hydrogen only occured when the electron dropped from a high energy level to a low energy level

james chadwick

Oct 20, 1891

james chadwickhe discovered part of the neutron and discovered the nucles.He bombarded the alpha rays coming out from a natural radioactive material onBeryllium atom and observed that Beryllium artificially became radioactive for a short time it emitted material rays

jj thompson

Feb 7, 1897

he researched cathode rays which led to the dicovery of the electron.
a href='http://http://www.biography.com/people/jj-thomson-40039' >jj thompson</a>he researched cathode rays which led to the dicovery of the electron.