Atomic Theories

He named the smallest piece of matter “atomos,” meaning “not to be cut.”

• Democritus

• John Dalton

• J.J. Thomson

• Ernest Rutherford

He proposed the Atomic Theory of Matter based on his experimental observations.

• Democritus

• John Dalton

• J.J. Thomson

• Ernest Rutherford

He proposed a model of atom which is known as Plum Pudding Model where the atom consists of a sphere of positive charge with negatively charged electron embedded in it.

• Democritus

• John Dalton

• J.J. Thomson

• Ernest Rutherford

Based on an experiment he realized that the atom must have almost all of its mass concentrated at its center, in a nucleus, with the vast majority of the atom consisting chiefly of empty space. His model is known as the Nuclear Model of the Atom.

• Democritus

• John Dalton

• J.J. Thomson

• Ernest Rutherford

He proposed the shell or planetary model of the atom: that electron moved around the nucleus in definite orbits.

• Ernest Rutherford

• Neils Bohr

• James Chadwick

• Eugen Goldstein

He proposed that the radiation that hit the paraffin plot until proton came out shows that atoms have other particles with a neutral electrical charge and the approximate mass of a proton, later known as neutron.

• Neils Bohr

• James Chadwick

• Eugen Goldstein

• Robert Millikan

He discovered that atoms have positive charges based on his experiment of anode rays (positive ray) and sometimes credited for the discovery of protons.

• Neils Bohr

• James Chadwick

• Eugen Goldstein

• Robert Millikan

He did the Oil-drop experiment, in which he was able to determine charge (e) of an electron.

• Neils Bohr

• James Chadwick

• Eugen Goldstein

• Robert Millikan

He theorizes that electrons move in waves, and they have no exact location and so he used mathematical equations to describe the likelihood of finding an electron in a certain position.

• Robert Millikan

• Erwin Schrodinger

• Neils Bohr

• Ernest Rtuherford

This model introduced the concept of sub-energy level where the nucleus is surrounded by an electron cloud. Area with most dense clouds has the probability of finding the electron is greatest.

• Plum Pudding model

• Planetary Model

• Quantum Mechanical Model

• Nuclear Model of the Atom