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427 BCE
Plato
He was an ancient Athenian philosopher most famously known for his philosophical texts. He proposed all matter was made up of elements and that atoms were shaped like triangles so they could connect. -
400 BCE
Democritus
He was an Ancient Greek philosopher who first proposed the atomic theory. He proposed that atoms were specific to the material they composed. He also said that atoms varied in size, were in constant motion, and could collide. -
500
The Alchemists
The Alchemists were a group of people who spent grueling hours trying to transmute metals into gold. They believed that all metals were made of two elements, mercury and sulfuric, in different ratios. Mercury had its essential properties of fluidity, fusibility, and malleability. Sulfur had its properties of combustibility, contributed body, and rusting. -
Robert Boyle
Robert Boyle was a chemist, alchemist, and physicist who created the now famously used Boyle's law. He proposed that everything was made of things called corpuscles that we now know are what are called atoms today. -
Antoine Lavoisier
He was a chemist and French nobleman who contributed to the chemical revolution. He did this by grouping elements into four groups: gases, metals, non-metals, and earthly substances. This helped make one of the first iterations of the periodic table by chemical properties. -
John Dalton
He was a chemist, physicist, and meteorologist. He was most famous for Dalton's atomic theory, which stated that matter was made up of tiny, indivisible atoms. It also stated that atoms of the same elements are the same. -
Billiard Ball Model
This Model said that atoms should combine and recombine to create compounds. It stated that atoms were solid spheres. It was made by John Dalton. -
Amedeo Avogadro
He was an Italian scientist who contributed to molecular theory. He created Avogadro's law which states that gases with the same volume, temperature, and pressure have the same number of molecules. -
Dmitri Mendeleev
He was a Russian chemist and inventor. He created a version of the periodic table where elements went by atomic weight. He also organized elements by chemical properties. -
Robert Millikan
He was an American experimental physicist. He was able to prove that electricity was conveyed by a minuscule unit, the electron -
JJ Thompson
He was a British physicist. He said atoms were made of smaller sub particles. He discovered the electron. -
Pierre and Marie Curie
They were Polish physicists and chemists. They Found the radioactive elements polonium and radium. In doing so, they also discovered radioactivity. -
Plum Pudding Model
This model stated that electrons were embedded in a sphere of positive charge Like blueberries in a muffin. Made by JJ Thompson. -
Albert Einstein
Albert Einstein was a German theoretical physicist who was one of the most influential scientists in the world. He was able to mathematically prove the existence of atoms and predict their size, and the size of molecules. -
Ernest Rutherford
He was a physicist from New Zealand and was called the father of nuclear physics. He theorized about the nucleus and how it had to be positively charged to balance out the charge of electrons. He established that most of the mass in an atom was in the nucleus. -
Neils Bohr
He was a Danish physicist who proposed a theory for the hydrogen atom based on the fact that some physical quantities only take discrete values. He also discovered how radiation worked in an atom. He proposed that when an electron moves from a higher energy orbit to a low energy one the difference in energy is sent out as radiation. -
Henry G.J. Mosely
He was an English physicist who contributed to physics and the periodic table. He created Mosley's law and created the atomic number system for the periodic table. -
Solar System Model
This model stated that electrons have a concentric orbit around the nucleus. It patterned the solar system. It was made by Neils Bohr. -
Werner Heisenberg
He was a German theoretical physicist who was one of the main pioneers of quantum theory. He was able to formulate a type of quantum mechanics based on matrices. -
Erwin Schödinger
He was an Irish physicist who found an equation that accurately found the energy level of an electron. He also created the electron cloud model around the same time -
Electron Cloud Model
The electron cloud model predicted the most likely location of an electron around an atom. It was created by Erwin Schrödinger. -
James Chadwich
He was an English physicist who inspired the U.S. to create the atomic bomb. He was able to do this by proving that neutrons exist.