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Period: 427 BCE to 347 BCE
Plato
He was an ancient Greek philosopher who introduced the atomic theory. He suggested the atoms all break down into different 3D shapes such as cubes pyramids et cetera. -
400 BCE
Democritus
He was an ancient Greek philosopher who helped develop the atomic theory (of the universe). He stated that everything is made up of atoms, these atoms are physically indivisible, there is empty space that exists between atoms, atoms cannot be destroyed, atoms are in perpetual motion and will always be, there are an infinite type and number of atoms, and these differ in size and shape. -
5 BCE
The Alchemists
Atomic theories were first introduced by Leucippus.
He stated that matter was eternal, things are made up of small indivisible particles, the particles are in constant motions and that they come in different shapes and sizes. -
Robert Boyle
He was an English-Irish scientist who formulated Boyle's (/Mariolle's) Law. It stated that the compression or expansion of gas at a constant temperature effect its density. -
Antone Lavoisier
He was a French chemist who created the Law of Conservation. It is that matter is neither destroyed nor created it can only be rearranged but can never disappear. -
John Dalton
He was a British physicist and chemist who created the first modern atomic theory. He stated that all matter is made up of tiny individual particles (atoms) with different masses and properties per element. -
Billiard Ball Model
It was created by John Dalton, a British chemist and physicist. The model defined an atom as a ball-like structure (as the concepts of the atomic nucleus and electrons were unknown at the time). -
Amedeo Avogrado
He was an Italian physicist and chemist who proposed Avogrado's Law. He stated that equal volumes of gases at equal temperature and pressure contain the same number of particles. In recognition of him, the number of molecules in a mole was named Avogrado's Number or Constant. -
Amedeo Avogrado
He was an Italian physicist and chemist. He also defined the atom as the smallest particle of an element that may or may not exist independently and a molecule as the smallest part of a substance that cannot exist on its own. -
Dmitri Mendeleev
He was a Russian chemist who created the framework for the Periodic Table. He managed to correctly predict the properties of unknown elements at his time. -
JJ Thompson
He was a British physicist who discovered the electron. This was the first subatomic particle to be discovered! -
Solar System Model
It was created by the Northern Irish physicist Joseph Lamor. It suggested that the central charge of an atom might be 'proportional' to its atomic mass in hydrogen units. -
Pierre and Marie Curie
He was a New Zealand physicist, and she was a Polish physicist and chemist. They hypothesized that radioactive particles cause atoms to break down and release radiation. They both shared half a Nobel Prize. -
Pierre and Marie Curie
He was a New Zealand physicist, and she was a Polish physicist and chemist. They discovered radium and polonium. They were the first radioactive elements to be discovered. Unfortunately, they did not know how dangerous radiation was and their continued experimentation with it led to their deaths. -
Plum Pudding Model
It was created by the British physicist JJ Thompson. It is a model of an atom presented as a sphere of equally distributed positive charge. -
Albert Einstein
He was a German-born theoretical physicist who further developed the model of an atom. He managed to prove the existence of atoms therefore giving much evidence ehind the atomic theory. -
Robert Millikan
He was an American physicist who helped further develop the atomic theory. He revealed that protons, in atoms, have an electric charge. -
Ernest Rutherford
He was a New Zealand physicist who did research on atomic physics. He discovered that atoms are mostly empty space. He is also often referred to as the "father of nuclear physics". -
Neils Bohr
He was a Danish physicist who further developed the model of an atom. He created it by adapting Ernest Rutherford's model and applying Planck's quantum theory which he then named it the Bohr Model. -
Henry G. J. Mosely
He was an English physicist who demonstrated the major properties of an atom are affected by its atomic number. He used x-rays to experiment. -
Electron Cloud Model
It was created by the Austrian physicist, Erwin Schroedinger. It is a model of an atom that shows the probable locations of electrons around the nucleus. -
James Chadwick
He was a British physicist who discovered the neutron. As a result, he won a Noble prize and was knighted.