-
460 BCE
Democritus
Democritus born. Was a Greek Philosopher who often questioned what we're made of. -
400 BCE
Democritus develops earliest atomic theory
In 400 B.C Democritus came up with a new atomic theory. He believed everything is composed of “atoms”, which are physically, but not geometrically, indivisible. Between atoms, there lies empty space, and atoms are indestructible. According to him. Atoms have always been, and always will be, in motion. Finally he believed that there are an infinite number of atoms, and kinds of atoms, which differ in shape, and size. -
John Dalton
John Dalton is born. He became an English chemist, physicist and meteorologist -
John Dalton's New Theory/Experiment
Dalton based his theory on the law of conservation of mass and the law of constant composition. The first part of his theory states that all matter is made of atoms, which are indivisible. The second part of the theory says all atoms of a given element are identical in mass and properties. The third part says compounds are combinations of two or more different types of atoms. He knew this by his experiment combining hydrogen and oxygen atoms. -
JJ Thompson
JJ Thompson birth, became a physicist and chemist. -
Ernest Rutherford
Rutherford Born, was a nuclear physicist. -
Niels Bohr Born
Niels Henrik David Bohr was a Danish physicist who made foundational contributions to understanding atomic structure and quantum theory, for which he received the Nobel Prize in Physics in 1922 -
Erwin Schrodinger Born
Erwin Rudolf Josef Alexander Schrödinger, sometimes written as Erwin Schrodinger or Erwin Schrodinger, was a Nobel Prize-winning Austrian physicist who developed a number of fundamental results in the field of quantum physics. -
JJ Thompson Experiment
Thompson used a cathode tube to put a high voltage electric arch and used that by seeing how much it attracted or repelled certain materials and found out that there are positive and negatively charged particles, thus leading to the finding of the electron. -
Plum Pudding Model
Thompson believed the atom to be very similar to plum pudding, mostly empty space with electrons floating throughout positively charged matter. -
Gold Foil Experiment
Rutherford conducted an experiment in which he shot alpha particles at a sheet of gold foil, and found that they shot out in different directions than they entered in. He found that the nuclei deflected each particle and sent them off in a different angle. -
The Atomic Model
Rutherford created a new atomic model. It consists of orbiting electrons (negative) around a nucleus containing protons (positive) and neutrons (neutral) -
Niels Bohr Electron Model
Niels Bohr proposed a theory for the hydrogen atom based on quantum theory that energy is transferred only in certain well defined quantities. Electrons should move around the nucleus but only in prescribed orbits. When jumping from one orbit to another with lower energy, a light quantum is emitted. -
Schrodinger Develops New Theory
This atomic model is known as the quantum mechanical model of the atom. Unlike the Bohr model, the quantum mechanical model does not define the exact path of an electron, but rather, predicts the odds of the location of the electron. Where the cloud is most dense, the probability of finding the electron is greatest, and conversely, the electron is less likely to be in a less dense area of the cloud. Thus, this model introduced the concept of sub-energy levels.
