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384 BCE
Plato
Plato is most famous for his writings "The Republic", which discusses society run by a philosopher. He's also known for speeches that which demonstrate his "metaphysical theory of forms". -
370 BCE
Democritus
Democritus was a philosopher that's from Ancient Greek times that is remembered today for a foundation of an atomic theory. Unfortunately, none of his work has survived. -
322 BCE
Aristotle
Aristotle was a Greek philosopher from the Classical period. Aristotle was taught by Plato and became the founder of the Peripatetic school of Philosophy. -
The Alchemists
The alchemists were a group of people that believed all metals were formed from mercury and sulfur. The Mercury provided the properties of fluidity and fusibility, and the Sulphur, gave the essential property of combustibility, contributed body and the ability to rust. -
Antione Lavoisier
Antoine Lavoisier was a French chemist who was crucial to the chemical revolution in the 1700's. He had a huge influence on the history of chemistry and biology. -
John Dalton
John Dalton is known for his theory that each element consists of its own unique and indivisible atom. He believed that atoms of one element are alike but are different from atoms of other elements. Dalton also gave atomic weights to the 20 elements he knew at the time -
Newland's Law of Octaves
This law states that chemical elements are arranged according to increasing atomic weight, and elements with similar physical and chemical properties occur after each interval of seven. -
Mendeleev's Pd. Table
Dmitri Mendeleev published a periodic table in 1869, and notably arranged the elements known at the time in order of atomic mass. -
Photoelectric Effect
Photoelectric Effect occurs when electrically charged particles are released from a material when it absorbs electromagnetic radiation. -
Discovery of Radioactivity
French physicist Henri Becquerel accidently discovered radioactivity in March of 1896. He opened a drawer and discovered spontaneous radioactivity. -
Discovery of the Elctron
For the final 20 years of the 19th century, scientists tried to discover the carrier of the electrical properties in matter. Their work ended when English physicist J.J. Thomson found the electron in 1897. -
Planck's Quantum Theory of Light
Planck's quantum theory states that light bulb filaments should be warmed to about 3,200 Kelvin to make sure most of the energy is emitted as visible waves. He believes that if heated much warmer, the ultraviolet light would cause negative effects. -
Plum Pudding Model
The plum pudding model is a model of the atom. The name comes from electrons surrounded by a positive charge, like negatively charged plums inside a positively charged “pudding." -
Rutherford's Gold Foil Experiment
A piece of gold foil was hit with particles that have a positive charge. Most particles went through the foil, showing that the gold atoms contained mostly empty space. -
Bohr's Planetary Model
The Bohr Model is a structural model of an atom. In this model, the electrons are placed around the nucleus in circular paths of movement. -
Mosley's Atomic Numbers
Moseley published a paper in where he believed the atomic number is the number of positive charges in the atomic nucleus. -
Discovery of the Proton
The proton was discovered by Ernest Rutherford in the early 1900's. His research ended in a reaction with the first splitting of the atom. This is how he discovered protons. -
Charge of the Electron
Electrons have an electric charge of −1 and their mass is approximately about 1/2000 the mass of a neutron or proton. Electron charge is usually denoted by the symbol e. -
Schrodinger Equation
The Schrödinger equation is an equation that outlines the wave function of a quantum-mechanical system. It is necessary in quantum mechanics. -
Heisenberg's Uncertainty Principle
The uncertainty principle states that we can't know both the position and speed of a particle with 100% accuracy. -
Discovery of the Neutron
In May 1932, James Chadwick announced that there was actually a new uncharged particle, which he called the neutron. -
Robert Millikan
Robert Millikan was a physicist that won the Nobel Prize for Physics in 1923. He was nominated for the award for measurement of the electric charge and for work on the photoelectric effect.