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427 BCE
Plato
He theorizes that these solid forms of matter are composed of indivisible elements (thecollecter.com) -
400 BCE
Democritus
He theorized that all material bodies are made up of indivisibly small atoms (britamica.com) -
300 BCE
The Alchemists
The Alchemists believed that all metals here formed from 2 principles such as mercury and sulfer (uwaterloo.com) -
230 BCE
Solar System Model
Where the sun is the center of the universe (education.com) -
Robert Boyle
He demonstarted that matter is made of tiny particles that he called corpuscle, but that are known as atoms today. (study.com) -
Antone Lavoisier
He defined the law of conversation of mass (study.com) -
John Dalton
He suggested that all matter was comprised of indivisible and indestructible atoms with district masses and properties (royalsociety.com) -
Billiard Ball Model
This defined an atom to be like a ball-like structure (ck12.org) -
Amedeo Avogadro
He realized that equal volumes of gas contain equal numbers of molecules and that elementary gasses such as hydrogen, nitrogen, and oxygen were composed of two atoms (lemoyne.edu) -
Dmitri Mendeleev
He discovered what is called the periodic table (khanacademy.org) -
JJ Thompson
He proposed the plum pudding model of the atomy which had negatively-charged electrons embedded within a positively charged soup (khanacademy.org) -
Pierre and Marie Curie
They discovered the strongly radioactive elements polonium and radium (Briannica.com) -
Electron Cloud Model
The area around an atom's nucleus where electrons are most likely to be found (universetoday.com) -
Plum Pudding Model
The atom is a sphere of positive charge and negatively charged electrons are embedded in it to balance the total positive charge (britannica.com) -
Albert Einstein
He mathematically predicted the size of both atoms and molecules (ck12.com) -
Robert Millikan
He accurate determination of the charge carried by an electron, using the elegant falling-drop method (nobelrpize.org) -
Ernest Rutherford
He established that the mass of the atom is concentrated in it's nucleus (primaryconnections.org) -
Nelis Bohr
He proposed a theory for the hydrogen atom, based on quantum theory that some physical quantities only take discrete values (nobleprize.org) -
Henry G. J. Mosely
He arranged the elements in the periodic table accordingly to atomic number (study.com) -
James Chadwich
He discovered that atoms consisted not only protons and electrons but also neutrons (study.com)