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440 BCE
Plato
theorized that these solid forms of matter are composed of indivisible elements shaped like triangles. -
400 BCE
Democritus
believed that atoms were uniform, solid, hard, incompressible, and indestructible, and that they moved in infinite numbers through empty space until stopped. -
Antone Lavoisier
defined that matter was composed of atoms that were not created or destroyed during chemical reactions. -
Billiard Ball Model
defined an atom to be a ball-like structure -
Robert Boyle
demonstrated that matter is made up of tiny particles that he called corpuscles which is what we call an atom today. -
John Dalton
he thought that 1, elements consist of indivisible small particles and 2, all atoms of the same element are identical, and different atoms have different elements. -
Amedeo Avogadro
he had 2 hypotheses: (1) equal volume of gas contains equal number of molecules. (2) elementary gases such as hydrogen, nitrogen, etc. consist of 2 atoms. -
Dmitri Mendeleev
formed a new law and built a systematic table of all 70 elements known. -
Pierre and Marie Curie
suggested that powerful rays or energy, the polonium and radium gave off were actually particles from tiny atoms that were disinegrating inside elements. -
Solar System Model
describes atoms as consisting of a nucleus with a number of electrons in orbits around the nucleus. -
JJ Thompson
proposed a model of the atom in which negative electrons are scattered throughout a sphere of positive change. -
Plum Pudding Model
depicts the electrons as negatively-charged particles embedded in a sea of positive charges. -
Albert Einstein
mathematically proved the existence of atoms and their sizes. -
Robert Millikan
Millikan's work demonstrated that electrons did have a discrete, quantifiable change. -
Ernest Rutherford
described the atom as having a tiny, dense, and positively charged core called the nucleus. -
Neils Bohr
proposed a theory for the structure of atoms and the Bohr Model. -
Henry G. J. Mosely
formed the Mosely Law, that states that the square root of the frequency of the X-ray emitted by an atom is proportional to its atomic number. -
Electron Cloud Model
shows a particular area in which an electron is likely to be. -
James Chadwich
found that the atoms consisted of protons and electrons and another sub-atomic particle called the nucleus. -
The Alchemists
the alchemists believed that all metals were formed from 2 principles= mercury and sulfur