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460 BCE
Democritus
Discovered that atoms were tiny solid particles that were incompressible and indestructible and surrounded by empty space. (Information from britannica.com) -
427 BCE
Plato
He theorized that solid forms of matter are composed of indivisible elements shaped like triangles. (Information from sutori.com) -
760
The Alchemists
They conducted matter experiments and believed that all metals were made from two principles, mercury and sulfur. (Information from wikipedia.com -
Robert Boyle
Discovered that matter was made of tiny particles, and the volume of a gas is inversely proportional to it's pressure and vice versa. (Information from sciencehistory.org) -
Antone Lavoisier
Defined the Law Of Conservation Of Mass stated that combustion and respiration are caused by chemical reactions with an element he called oxygen. (Information from sciencehistory.org) -
John Dalton
He said that each element had one type of atom, and that all matter was made up of indivisible and indestructible atoms. (Information from britannica.com) -
Billiard Ball Model
Created by John Dalton and also referred to as the Dalton Model, defines an atom to be a ball-like structure, as the concepts of atomic nucleus and electrons were unknown at the time. (Information from brilliant.org) -
Amedeo Avogadro
He discovered that equal volumes of gas contain an equal number of molecules and elementary gases. He also discovered the elements Hydrogen (H), Nitrogen (N), and Oxygen (O) are composed of two atoms. (Information from lemoyne.edu) -
Dmitri Mendeleev
He is often referred as the father of the Periodic Table since he created it. (Information from scientist.com and rsc.org) -
JJ Thompson
He discovered the electron, a model of the atom in which negative electrons are scattered throughout a sphere of positive charge. (Information from ck12.org and sciencehistory.org -
Pierre and Marie Curie
They discovered that elements can be radioactive, and discovered the highly radioactive elements polonium (Po) and radium (Ra) (Information from britannica.com) -
Plum Pudding Model
Thomas Thomson developed what became known as the "plum pudding" model. Plum pudding is an English dessert similar to a blueberry muffin. In Thomson's plum pudding model of the atom, the electrons were embedded in a uniform sphere of positive charge, like blueberries stuck into a muffin. (Information from chem.libretexts.com) -
Albert Einstein
He mathematically proved that atoms existed and thus helped revolutionize all the sciences through the use of statistics and probability. (Information from ans.org) -
Robert Millikan
He discovered the magnitude of the electron's charge and did many experiments with oil and metal plates. (Information from nobelprize.com) -
Ernest Rutherford
He established that the mass of an atom was concentrated in the nucleus, and the lighter electrons revolved around the nucleus, much like a solar system. (Information from primaryconnections.org) -
Henry G. J. Mosely
He discovered that the nucleus was positively and found a way to organize the elements on the Periodic Table by atomic number, or the number of protons and electrons in that type of atom. (Information from britannica.com and study.com) -
Niels Bohr
He proposed a theory for the hydrogen atom, and the electron was able to occupy only certain orbits around the nucleus. (Information from nobelprize.com and britannica.com) -
Solar System Model
Also referred to as the Bohr Model, the Solar System Model describes atoms as consisting of a nucleus with a number of electrons in orbits around that nucleus, similar to a solar system. Because of this, people have speculated that perhaps atoms are like tiny solar systems. (Information from school-for-champions.com) -
Electron Cloud Model
Erwin Schrödinger created the electron cloud model. The model is a tool for visualizing the electron positions in an atom. (Information from vendantu.com) -
James Chadwick
He discovered that the nucleus of an atom not only contained protons, but also neutrons, subatomic particles with a neutral charge. (Information from britannica.com)