-
Period: 450 to
Atomic Theory
Something we had to do for school. -
470
Democritus (Greece)
Democritus - WikipediaTheorised that all matter was made up of atoms, and that each differed from each other in form, position and arrangement. -
Isaac Newton (England)
Newton - Scienceworld.WolframTheorised that different elements were made depending on the arrangement of the atom, and that atoms looked like small round billarad-like balls. He also theorised that atoms were held together by forces of attraction. -
John Dalton (England)
Dalton - WikipediaAtoms have a weight unique to an element and that all atoms of the same element are identical. Atoms can only be rearranged in a chemical reaction; not destroyed, created or separated into smaller particles. He came up with the Billard Ball model of an atom. -
George Johnstone Stoney (Ireland)
Stoney - UniversityscienceConcepted that electricity was made of negatively charged particles, later which he proposed to call electron.He also calculated the charge of an electron. -
Joseph John Thomson (England)
Thomson - ChemheritageFirst to discover electrons and isotopes. Proved the existance of subatomic particles through the use of cathode rays. Devised the plum-pudding model. -
Max Planck (Germany)
Planck - WikipediaExplained the glowing of hot matter with quanta; small discrete units of energy beging radiated from the matter. This lead to the quantum theory, revolutionising our study of the atom. -
Nagaoka Hantaro (Japan)
Nagaoka - WikipediaCreated the Saturian Model of the atom with rings of electrons around the nucleus; based on the planet, Saturn. Although many of the details were incorrect, it helped us understand the structure of an atom. -
Robert Andrews Millikan (USA)
Milikan - JuliantrubinConducted the Oil Drop Experiment, and used it to determine the charge and mass of an electron. -
Ernest Rutherford (England/New Zealand)
Rutherford - Chemistry.aboutDiscovered alpha and beta decay in radioactive materials. Used alpha particles to probe the atoms in a thin piece of gold foil. Established that the nucleus was very small, dense and positively charged. He also hypothesised the existance of neutrons but assumed that electrons were found in the nucleus, giving us the Planetary or Nuclear model. -
Henry Gwyn-Jeffreys Moseley (England)
Moseley - ChemistryexplainedDetermined the charge of most nuclei using X-ray. Determined that an element's atomic number and number of protons were equal, leading to the Periodic Table of Elements being arranged by atomic number instead of atomic mass. -
Niels Bohr (Denmark)
Bohr - WikipediaTheorised electrons travelled in orbit around the nucleus and created the Bohr Model of the atom after expanding on Rutherford's work. -
