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400 BCE
Democritus
Democritus was the person to bring up the idea of atoms. He said atoms make up everything. -
384 BCE
Aristotle
Aristotle described that everything in earth was made up of the four elements: wind, water, fire, and earth. He said all matter is made up of little indivisible particles called atoms. -
330 BCE
Plato
Plato said that there were 5 main solid shapes whose sides are made from polygons and the atom had to relate to them in some way. -
330 BCE
Solar System Model
Plato -
Robert Boyle
Boyle discovered that volume of gas directly connected to the increase and decrease in pressure. The higher pressure there was, the lower volume of gas there was. The lower pressure there was, the higher volume of gas there was. -
Lavoisier
Antoine Lavoisier discovered that the total mass of products and reactants in a chemical reaction are always the same. -
The Alchemists
The alchemists mixed different things with certain acid and saw how each reacted. With this they were able to start a foundation of what the periodic table is today. Although it was nothing like today, it was a very advanced for their time period. -
John Dalton
John Dalton discovered that all matter was made up of atoms. He also found that in the same element, all atoms are the same size but the size differs in different elements. -
Solid Sphere of "Billiard Ball" Model
John Dalton -
Dmitri Mandeleev
Mendeleev was the one who created the Mendeleev periodic table. He found that when you rearrange element in atomic weight going up, there are reoccurring patterns. -
J.J. Thomson
Thomson announced that he discovered that atoms were made up even smaller things. This changed how scientists viewed the atom. -
"Plum Pudding" Model
J.J. Thomson -
The Curies
Pierre and Marie Curie discovered two new elements called radium and polonium. Marie really brought up the term radioactivity in her discoveries. -
Planck's Quantum Theory of Light
Planck's Theory was that the energy of light is proportional to the frequency. -
Photoelectric Effect
The photoelectric effect is the different ways that electrons reflect light off different materials. After this process the result are photoelectrons. -
Albert Einstein
Einstein proved that the atom was real in 1905. Also at this time he discovered that atoms are always in constant, random motion. -
Robert Millikan
Using the oil drop experiment, Millikan was able to find the value for electron charge. -
Ernest Rutherford
He is known for the Gold Foil experiment. This model showed that the atom is a mostly empty space with a tiny, positively charged, nucleus inside of it. -
Neils Bohr
Neils Bohr proposed one of the most common atomic models there are: The Bohr model. This suggested that electrons made specific orbits around the nucleus of an atom. Each ring could hold a certain amount of electrons. -
Henry G.J. Moseley
Moseley was the person that discovered the atomic number of an element was equal to the amount of protons there were. This was a big milestone in finding out more about the atom. -
Schrodinger Equation
The Schrodinger Equation shows how certain small particles move. This equation shows how waves move those smaller particles. -
Electron Cloud Model
Erwin Schrodinger -
Werner Heisenberg
Werner discovered the uncertainty principle which stated that the position and momentum of a particle cannot be exactly found. In other words he's saying that electrons do not circle in perfect orbits. -
James Chadwick
James Chadwick discovered one of the most important things in the atom: The neutron. He found that it was in the atom and that it had no charge
