-
465
Democritus
BCE..first composed matter exists in forms of particles -
John Dalton
proposed atomic theory -
Dmitri Mendeleev
created first periodic table with elements divided into 7 groups. -
Ernest Rutherford
discovered half-life of radioactive elements. Established nucleus was small and dense. -
William Crookes
discovered cathode rays travel in straight lines. -
JJ Thompson
Discovered electrons using crookes tube. -
Neils Bohr
created bohr model of atom which shows electrons outside nucleus. -
James Chadwick
Discovered the electron.